Download and install OpenH264 GMP plugin when installing Firefox

[Pehrsons]

This patch adds a step to download the public OpenH264 GMP plugin from the Cisco CDN during Firefox installation . The correct version is parsed from openh264.json, which is downloaded for the corresponding revision from the Firefox github. The plugin is extracted into the correct folder structure "gmp-gmpopenh264/{version}" inside "browsers/{channel}".

In Firefox.setup_kwargs, the presence of this folder is detected and used to set the environment variable MOZ_GMP_PATH down the line.

This makes OpenH264 available to WebRTC tests, allowing those reliant on H264 to pass.

[jgraham]

So basically I think this looks fine, but I was initially a bit confused about the use of the FirefoxPrefs class to do something unrelated to prefs. Could we clean it up with something like the following:

diff --git a/tools/wpt/browser.py b/tools/wpt/browser.py
index 7fae46a5e88..4f7b5576156 100644
--- a/tools/wpt/browser.py
+++ b/tools/wpt/browser.py
@@ -12,7 +12,7 @@ import tempfile
 from abc import ABCMeta, abstractmethod
 from datetime import datetime, timedelta, timezone
 from shutil import which
-from typing import Any, Dict, List, Optional, Tuple
+from typing import Any, Dict, List, Optional, Tuple, Mapping
 from urllib.parse import urlsplit, quote
 
 import html5lib
@@ -201,27 +201,12 @@ class Browser(metaclass=ABCMeta):
         return NotImplemented
 
 
-class FirefoxPrefs:
+class FirefoxVcsResources:
     def __init__(self, logger):
         self.logger = logger
 
     def install_prefs(self, binary: Optional[str], dest: Optional[str] = None, channel: Optional[str] = None) -> str:
-        if binary and not binary.endswith(".apk"):
-            version, channel_, rev = self.get_version_and_channel(binary)
-            if channel is not None and channel != channel_:
-                # Beta doesn't always seem to have the b in the version string, so allow the
-                # manually supplied value to override the one from the binary
-                self.logger.warning("Supplied channel doesn't match binary, using supplied channel")
-            elif channel is None:
-                channel = channel_
-        else:
-            rev = None
-            version = None
-
-        if channel is None:
-            self.logger.warning("No browser channel passed to install_prefs, taking prefs from main branch")
-            channel = "nightly"
-
+        version, channel, rev = self.get_version_and_channel(binary, channel)
         if dest is None:
             dest = os.curdir
 
@@ -250,6 +235,24 @@ class FirefoxPrefs:
 
         return dest
 
+    def get_openh264_data(self, binary: Optional[str], channel: Optional[str]) -> Optional[Mapping[str, Any]]:
+        version, channel, rev = self.get_version_and_channel(binary, channel)
+        ref = self.get_git_ref(version, channel, rev)
+        self.logger.info("Downloading openh264.json from git ref %s" % ref)
+        try:
+            openh264_json: Mapping[str, Any] = json.loads(
+                get_file_github(
+                    "mozilla-firefox/firefox",
+                    ref,
+                    "toolkit/content/gmp-sources/openh264.json",
+                )
+            )
+        except Exception as e:
+            self.logger.warning("Failed to download openh264.json: %s" % e)
+            return None
+
+        return openh264_json
+
     def get_profile_github(self, version: Optional[str], channel: str, dest: str, rev: Optional[str]) -> None:
         """Read the testing/profiles data from firefox source on GitHub"""
 
@@ -284,7 +287,26 @@ class FirefoxPrefs:
             with open(dest_path, "wb") as f:
                 f.write(data)
 
-    def get_version_and_channel(self, binary: str) -> Tuple[Optional[str], str, Optional[str]]:
+    def get_version_and_channel(self, binary: Optional[str], channel: Optional[str]) -> tuple[Optional[str], str, Optional[str]]:
+        if binary and not binary.endswith(".apk"):
+            version, channel_, rev = self.get_binary_version_and_channel(binary)
+            if channel is not None and channel != channel_:
+                # Beta doesn't always seem to have the b in the version string, so allow the
+                # manually supplied value to override the one from the binary
+                self.logger.warning("Supplied channel doesn't match binary, using supplied channel")
+            elif channel is None:
+                channel = channel_
+        else:
+            rev = None
+            version = None
+
+        if channel is None:
+            self.logger.warning("Unable to resolve browser channel, using nightly")
+            channel = "nightly"
+
+        return version, channel, rev
+
+    def get_binary_version_and_channel(self, binary: str) -> Tuple[Optional[str], str, Optional[str]]:
         application_ini_path = os.path.join(os.path.dirname(binary), "application.ini")
         if os.path.exists(application_ini_path):
             try:
@@ -396,7 +418,10 @@ class FirefoxPrefs:
         return max(tags)[1]
 
 
-class FirefoxAndroidPrefs(FirefoxPrefs):
+class FirefoxAndroidVcsResources(FirefoxVcsResources):
+    def get_openh264_data(self, binary: Optional[str], channel: Optional[str]) -> Optional[Mapping[str, Any]]:
+        raise NotImplementedError
+
     def get_git_ref(self, version: Optional[str], channel: str, rev: Optional[str]) -> str:
         if rev is not None:
             return rev
@@ -555,23 +580,9 @@ class Firefox(Browser):
             )
             return None
 
-        prefs = FirefoxPrefs(self.logger)
-        version, channel_, rev = (
-            prefs.get_version_and_channel(binary) if binary else (None, channel, None)
-        )
-        ref = prefs.get_git_ref(version, channel_ if channel is None else channel, rev)
+        openh264_json = FirefoxVcsResources(self.logger).get_openh264_data(binary, channel)
 
-        self.logger.info("Downloading openh264.json from git ref %s" % ref)
-        try:
-            openh264_json = json.loads(
-                get_file_github(
-                    "mozilla-firefox/firefox",
-                    ref,
-                    "toolkit/content/gmp-sources/openh264.json",
-                )
-            )
-        except Exception as e:
-            self.logger.warning("Failed to download openh264.json: %s" % e)
+        if openh264_json is None:
             return None
 
         version = openh264_json["vendors"]["gmp-gmpopenh264"]["version"]
@@ -623,7 +634,7 @@ class Firefox(Browser):
         return openh264_dir
 
     def install_prefs(self, binary, dest=None, channel=None):
-        return FirefoxPrefs(self.logger).install_prefs(binary, dest, channel)
+        return FirefoxVcsResources(self.logger).install_prefs(binary, dest, channel)
 
     def find_binary_path(self, path=None, channel="nightly"):
         """Looks for the firefox binary in the virtual environment"""
@@ -810,7 +821,7 @@ class FirefoxAndroid(Browser):
         return self.download(dest, channel)
 
     def install_prefs(self, binary, dest=None, channel=None):
-        return FirefoxAndroidPrefs(self.logger).install_prefs(binary, dest, channel)
+        return FirefoxAndroidVcsResources(self.logger).install_prefs(binary, dest, channel)
 
     def find_binary(self, venv_path=None, channel=None):
         return self.apk_path