Finish some screenshot refactors (#2394)

* finish refactor

* Docs changes

---------

Co-authored-by: GitHub Action <[email protected]>

Author: kblok

README.md

@@ -60,7 +60,7 @@ await using var page = await browser.NewPageAsync();
 await page.GoToAsync("http://www.google.com");
 await page.ScreenshotAsync(outputFile);
 ```
-<sup><a href='https://github.com/hardkoded/puppeteer-sharp/blob/master/lib/PuppeteerSharp.Tests/ScreenshotTests/PageScreenshotTests.cs#L61-L69' title='Snippet source file'>snippet source</a> | <a href='#snippet-screenshotasync' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/hardkoded/puppeteer-sharp/blob/master/lib/PuppeteerSharp.Tests/ScreenshotTests/PageScreenshotTests.cs#L55-L63' title='Snippet source file'>snippet source</a> | <a href='#snippet-screenshotasync' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 You can also change the view port before generating the screenshot
@@ -74,7 +74,7 @@ await Page.SetViewportAsync(new ViewPortOptions
     Height = 500
 });
 ```
-<sup><a href='https://github.com/hardkoded/puppeteer-sharp/blob/master/lib/PuppeteerSharp.Tests/ScreenshotTests/ElementHandleScreenshotTests.cs#L19-L25' title='Snippet source file'>snippet source</a> | <a href='#snippet-setviewportasync' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/hardkoded/puppeteer-sharp/blob/master/lib/PuppeteerSharp.Tests/ScreenshotTests/ElementHandleScreenshotTests.cs#L15-L21' title='Snippet source file'>snippet source</a> | <a href='#snippet-setviewportasync' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 ### Generate PDF files

lib/PuppeteerSharp.Tests/ScreenshotTests/ElementHandleScreenshotTests.cs

@@ -8,10 +8,6 @@ namespace PuppeteerSharp.Tests.ScreenshotTests
 {
     public class ElementHandleScreenshotTests : PuppeteerPageBaseTest
     {
-        public ElementHandleScreenshotTests(): base()
-        {
-        }
-
         [PuppeteerTest("screenshot.spec.ts", "ElementHandle.screenshot", "should work")]
         [PuppeteerTimeout]
         public async Task ShouldWork()
@@ -149,7 +145,7 @@ public async Task ShouldFailToScreenshotADetachedElement()
             await Page.EvaluateFunctionAsync("element => element.remove()", elementHandle);
 
             var exception = Assert.ThrowsAsync<PuppeteerException>(elementHandle.ScreenshotStreamAsync);
-            Assert.AreEqual("Node is either not visible or not an HTMLElement", exception.Message);
+            Assert.AreEqual("Node is either not visible or not an HTMLElement", exception!.Message);
         }
 
         [PuppeteerTest("screenshot.spec.ts", "ElementHandle.screenshot", "should not hang with zero width/height element")]
@@ -159,7 +155,7 @@ public async Task ShouldNotHangWithZeroWidthHeightElement()
             await Page.SetContentAsync(@"<div style='width: 50px; height: 0'></div>");
             var elementHandle = await Page.QuerySelectorAsync("div");
             var exception = Assert.ThrowsAsync<PuppeteerException>(elementHandle.ScreenshotDataAsync);
-            Assert.AreEqual("Node has 0 height.", exception.Message);
+            Assert.AreEqual("Node has 0 height.", exception!.Message);
         }
 
         [PuppeteerTest("screenshot.spec.ts", "ElementHandle.screenshot", "should work for an element with fractional dimensions")]