fix(icon): stop breaking id references when caching icon ids (#11342)

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## PR Checklist
Please check that your PR fulfills the following requirements:
- [x] The commit message follows [our guidelines](https://github.com/angular/material/blob/master/.github/CONTRIBUTING.md#-commit-message-format)
- [x] Tests for the changes have been added or this is not a bug fix / enhancement
- [x] Docs have been added, updated, or were not required

## PR Type
What kind of change does this PR introduce?
<!-- Please check the one that applies to this PR using "x". -->
```
[x] Bugfix
[ ] Enhancement
[x] Documentation content changes
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Infrastructure changes
[ ] Other... Please describe:
```

## What is the current behavior?
SVGs with embedded `id`s can be broken when they are read out of the icon cache.

<!-- Please describe the current behavior that you are modifying and link to one or more relevant issues. -->
Issue Number: 
Fixes #8689

## What is the new behavior?
SVGs with embedded `id`s can be read out of the icon cache without breaking because the `id` references are now updated in addition to the `id`s themselves.

## Does this PR introduce a breaking change?
```
[ ] Yes
[x] No
```
<!-- If this PR contains a breaking change, please describe the impact and migration path for existing applications below. -->
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## Other information
Thanks to @ystreibel for starting this work in #11315!

Author: Splaktar

src/components/icon/demoLoadSvgIconsFromUrl/script.js

@@ -1,9 +1,8 @@
-
 angular.module('appSvgIconSets', ['ngMaterial'])
   .controller('DemoCtrl', function($scope) {})
-  .config(['$mdIconProvider', function($mdIconProvider) {
+  .config(function($mdIconProvider) {
     $mdIconProvider
       .iconSet('social', 'img/icons/sets/social-icons.svg', 24)
       .iconSet('symbol', 'img/icons/sets/symbol-icons.svg', 24)
       .defaultIconSet('img/icons/sets/core-icons.svg', 24);
-  }]);
+  });

src/components/icon/demoSvgIconSets/script.js

@@ -1,18 +1,13 @@
-
 angular.module('appUsingTemplateCache', ['ngMaterial'])
   .controller('DemoCtrl', function($scope) {})
   .config(function($mdIconProvider) {
-
     // Register icon IDs with sources. Future $mdIcon( <id> ) lookups
     // will load by url and retrieve the data via the $templateRequest
-
     $mdIconProvider
-      .iconSet('core', 'img/icons/sets/core-icons.svg',24)
-      .icon('social:cake', 'img/icons/cake.svg',24);
-
+      .iconSet('core', 'img/icons/sets/core-icons.svg', 24)
+      .icon('social:cake', 'img/icons/cake.svg', 24);
   })
   .run(function($templateRequest) {
-
     var urls = [
       'img/icons/sets/core-icons.svg',
       'img/icons/cake.svg',
@@ -21,10 +16,7 @@ angular.module('appUsingTemplateCache', ['ngMaterial'])
 
     // Pre-fetch icons sources by URL and cache in the $templateCache...
     // subsequent $templateRequest calls will look there first.
-
     angular.forEach(urls, function(url) {
       $templateRequest(url);
     });
-
-  })
-  ;
+  });

src/components/icon/demoUsingTemplateRequest/script.js

@@ -419,6 +419,11 @@ describe('MdIcon service', function() {
     $scope = $rootScope;
 
     $templateCache.put('android.svg'    , '<svg><g id="android"></g></svg>');
+    $templateCache.put('angular-logo.svg',
+      '<svg><g id="angular"></g><defs><filter id="shadow"></filter>' +
+      '<g id="bg" fill="#000000"><path d="M10 10"/></g></defs>' +
+      '<path filter="url(#shadow)"></path><use x="0" y="0" xlink:href="#bg"></use>' +
+      '</svg>');
     $templateCache.put('social.svg'     , '<svg><g id="s1"></g><g id="s2"></g></svg>');
     $templateCache.put('symbol.svg'     , '<svg><symbol id="s1"></symbol><symbol id="s2" viewBox="0 0 32 32"></symbol></svg>');
     $templateCache.put('core.svg'       , '<svg><g id="c1"></g><g id="c2" class="core"></g></svg>');
@@ -587,6 +592,25 @@ describe('MdIcon service', function() {
 
         $scope.$digest();
       });
+
+      it('should suffix duplicated ids and refs', function() {
+        // Just request the icon to be stored in the cache.
+        $mdIcon('angular-logo.svg');
+
+        $scope.$digest();
+
+        $mdIcon('angular-logo.svg').then(function(el) {
+          expect(el.querySelector('defs').firstChild.id).toMatch(/.+_cache\d+/g);
+          expect(el.querySelectorAll('path')[1].attributes.filter.value.split(/url\(#(.*)\)$/g)[1])
+            .toMatch(/.+_cache[0-9]+/g);
+          expect(el.querySelectorAll('path')[1].attributes.filter.value.split(/url\(#(.*)\)$/g)[1])
+            .toEqual(el.querySelector('defs').firstChild.id);
+          expect(el.querySelector('use').attributes['xlink:href'].value.split(/#(.*)/)[1]).toEqual(
+            el.querySelector('defs').children[1].id);
+        });
+
+        $scope.$digest();
+      });
     });
 
     describe('icon in a group is not found', function() {

src/components/icon/icon.spec.js

@@ -24,28 +24,11 @@ angular
  * `md-icon` lets you consume an icon font by letting you reference specific icons in that font
  * by name rather than character code.
  *
- * ### SVG
- * For SVGs, the problem with using `<img>` or a CSS `background-image` is that you can't take
- * advantage of some SVG features, such as styling specific parts of the icon with CSS or SVG
- * animation.
- *
- * `md-icon` makes it easier to use SVG icons by *inlining* the SVG into an `<svg>` element in the
- * document. The most straightforward way of referencing an SVG icon is via URL, just like a
- * traditional `<img>`. `$mdIconProvider`, as a convenience, lets you _name_ an icon so you can
- * reference it by name instead of URL throughout your templates.
- *
- * Additionally, you may not want to make separate HTTP requests for every icon, so you can bundle
- * your SVG icons together and pre-load them with $mdIconProvider as an icon set. An icon set can
- * also be given a name, which acts as a namespace for individual icons, so you can reference them
- * like `"social:cake"`.
- *
- * When using SVGs, both external SVGs (via URLs) or sets of SVGs [from icon sets] can be
- * easily loaded and used. When using font-icons, developers must follow three (3) simple steps:
+ * When using font-icons, developers must follow three (3) simple steps:
  *
  * <ol>
  * <li>Load the font library. e.g.<br/>
- *    `<link href="https://fonts.googleapis.com/icon?family=Material+Icons"
- *    rel="stylesheet">`
+ *    `<link href="https://fonts.googleapis.com/icon?family=Material+Icons" rel="stylesheet">`
  * </li>
  * <li>
  *   Use either (a) font-icon class names or (b) a fontset and a font ligature to render the font glyph by
@@ -63,26 +46,36 @@ angular
  * </li>
  * </ol>
  *
- * Full details for these steps can be found:
+ * Full details for these steps can be found in the
+ * <a href="http://google.github.io/material-design-icons/#icon-font-for-the-web" target="_blank">
+ * Material Design Icon font for the web docs</a>.
  *
- * <ul>
- * <li>http://google.github.io/material-design-icons/</li>
- * <li>http://google.github.io/material-design-icons/#icon-font-for-the-web</li>
- * </ul>
+ * You can browse and search the Material Design icon style <code>.material-icons</code>
+ * in the <a href="https://material.io/tools/icons/" target="_blank">Material Design Icons tool</a>.
  *
- * The Material Design icon style <code>.material-icons</code> and the icon font references are published in
- * Material Design Icons:
+ * ### SVG
+ * For SVGs, the problem with using `<img>` or a CSS `background-image` is that you can't take
+ * advantage of some SVG features, such as styling specific parts of the icon with CSS or SVG
+ * animation.
  *
- * <ul>
- * <li>https://design.google.com/icons/</li>
- * <li>https://design.google.com/icons/#ic_accessibility</li>
- * </ul>
+ * `md-icon` makes it easier to use SVG icons by *inlining* the SVG into an `<svg>` element in the
+ * document. The most straightforward way of referencing an SVG icon is via URL, just like a
+ * traditional `<img>`. `$mdIconProvider`, as a convenience, lets you _name_ an icon so you can
+ * reference it by name instead of URL throughout your templates.
+ *
+ * Additionally, you may not want to make separate HTTP requests for every icon, so you can bundle
+ * your SVG icons together and pre-load them with `$mdIconProvider` as an icon set. An icon set can
+ * also be given a name, which acts as a namespace for individual icons, so you can reference them
+ * like `"social:cake"`.
+ *
+ * When using SVGs, both external SVGs (via URLs) or sets of SVGs (from icon sets) can be
+ * easily loaded and used.
  *
  * ### Localization
  *
- * Because an `md-icon` element's text content is not intended to be translated, it is recommended to declare the text
- * content for an `md-icon` element in its start tag. Instead of using the HTML text content, consider using `ng-bind`
- * with a scope variable or literal string.
+ * Because an `md-icon` element's text content is not intended to be translated, it is recommended
+ * to declare the text content for an `md-icon` element in its start tag. Instead of using the HTML
+ * text content, consider using `ng-bind` with a scope variable or literal string.
  *
  * Examples:
  *
@@ -91,20 +84,25 @@ angular
  *   <li>`<md-icon ng-bind="'menu'"></md-icon>`
  * </ul>
  *
- * <h2 id="material_design_icons">Material Design Icons</h2>
- * Using the Material Design Icon-Selector, developers can easily and quickly search for a Material Design font-icon and
- * determine its textual name and character reference code. Click on any icon to see the slide-up information
- * panel with details regarding a SVG download or information on the font-icon usage.
+ * <h2 id="material_design_icons">Material Design Icons tool</h2>
+ * Using the Material Design Icons tool, developers can easily and quickly search for a specific
+ * open source Material Design icon. The search is in the top left. Below search, you can select
+ * from the new icon themes or filter by icon category.
  *
- * <a href="https://material.io/tools/icons/?icon=accessibility&style=baseline" target="_blank" style="border-bottom:none;">
- * <img src="https://cloud.githubusercontent.com/assets/210413/7902490/fe8dd14c-0780-11e5-98fb-c821cc6475e6.png"
- *      aria-label="Material Design Icon-Selector" style="max-width:75%;padding-left:10%">
+ * <a href="https://material.io/tools/icons/" target="_blank" style="border-bottom:none;">
+ * <img src="https://user-images.githubusercontent.com/3506071/41942584-ef0695d0-796d-11e8-9436-44f25023a111.png"
+ *      aria-label="Material Design Icons tool" style="max-width:95%">
  * </a>
  *
- * <span class="image_caption">
- *  Click on the image above to link to the
- *  <a href="https://design.google.com/icons/#ic_accessibility" target="_blank">Material Design Icon-Selector</a>.
- * </span>
+ * <div class="md-caption" style="text-align: center; margin-bottom: 24px">
+ *  Click on the image above to open the
+ *  <a href="https://material.io/tools/icons/" target="_blank">Material Design Icons tool</a>.
+ * </div>
+ *
+ * Click on any icon, then click on the "Selected Icon" chevron to see the slide-up
+ * information panel with details regarding a SVG download and information on the font-icon's
+ * textual name. This panel also allows you to select a black on transparent or white on transparent
+ * icon and to change the icon size. These settings only affect the downloaded icons.
  *
  * @param {string} md-font-icon String name of CSS icon associated with the font-face will be used
  * to render the icon. Requires the fonts and the named CSS styles to be preloaded.
@@ -128,34 +126,35 @@ angular
  * When using SVGs:
  * <hljs lang="html">
  *
- *  <!-- Icon ID; may contain optional icon set prefix; icons must registered using $mdIconProvider -->
- *  <md-icon md-svg-icon="social:android"    aria-label="android " ></md-icon>
+ *<!-- Icon ID; may contain optional icon set prefix.
+ *     Icons must be registered using $mdIconProvider. -->
+ *<md-icon md-svg-icon="social:android"    aria-label="android " ></md-icon>
  *
- *  <!-- Icon urls; may be preloaded in templateCache -->
- *  <md-icon md-svg-src="/android.svg"       aria-label="android " ></md-icon>
- *  <md-icon md-svg-src="{{ getAndroid() }}" aria-label="android " ></md-icon>
+ *<!-- Icon urls; may be preloaded in templateCache -->
+ *<md-icon md-svg-src="/android.svg"       aria-label="android " ></md-icon>
+ *<md-icon md-svg-src="{{ getAndroid() }}" aria-label="android " ></md-icon>
  *
  * </hljs>
  *
  * Use the <code>$mdIconProvider</code> to configure your application with
- * svg iconsets.
+ * SVG icon sets.
  *
  * <hljs lang="js">
- *  angular.module('appSvgIconSets', ['ngMaterial'])
- *    .controller('DemoCtrl', function($scope) {})
- *    .config(function($mdIconProvider) {
- *      $mdIconProvider
- *         .iconSet('social', 'img/icons/sets/social-icons.svg', 24)
- *         .defaultIconSet('img/icons/sets/core-icons.svg', 24);
- *     });
+ * angular.module('appSvgIconSets', ['ngMaterial'])
+ *   .controller('DemoCtrl', function($scope) {})
+ *   .config(function($mdIconProvider) {
+ *     $mdIconProvider
+ *       .iconSet('social', 'img/icons/sets/social-icons.svg', 24)
+ *       .defaultIconSet('img/icons/sets/core-icons.svg', 24);
+ *    });
  * </hljs>
  *
  *
  * When using Font Icons with classnames:
  * <hljs lang="html">
  *
- *  <md-icon md-font-icon="android" aria-label="android" ></md-icon>
- *  <md-icon class="icon_home"      aria-label="Home"    ></md-icon>
+ * <md-icon md-font-icon="android" aria-label="android" ></md-icon>
+ * <md-icon class="icon_home" aria-label="Home"></md-icon>
  *
  * </hljs>
  *