WebShare: Add Feature Flag

Adding a new feature flag to allow enabling the WebShare functionality
on the platforms (OS and Chrome OS) where it is being actively
developed.

http://crbug.com/1035527

Change-Id: I5cd9274457c86c957360ff7e6a0b61f1c474e124
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2357091Reviewed-by: Eric Willigers <ericwilligers@chromium.org>
Commit-Queue: Hoch Hochkeppel <mhochk@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#798717}

chrome/browser/about_flags.cc

@@ -3081,6 +3081,11 @@ const FeatureEntry kFeatureEntries[] = {
      flag_descriptions::kMacV2GPUSandboxDescription, kOsMac,
      FEATURE_VALUE_TYPE(features::kMacV2GPUSandbox)},
 #endif  // OS_MAC
+#if defined(OS_CHROMEOS) || defined(OS_WIN)
+    {"web-share", flag_descriptions::kWebShareName,
+     flag_descriptions::kWebShareDescription, kOsWin | kOsCrOS,
+     FEATURE_VALUE_TYPE(features::kWebShare)},
+#endif  // OS_CHROMEOS || OS_WIN
 #if BUILDFLAG(ENABLE_VR)
     {"webxr-incubations", flag_descriptions::kWebXrIncubationsName,
      flag_descriptions::kWebXrIncubationsDescription, kOsAll,

chrome/browser/flag-metadata.json

@@ -4501,6 +4501,11 @@
     "owners": [ "ayui", "goto" ],
     "expiry_milestone": 86
   },
+  {
+    "name": "web-share",
+    "owners": [ "mhochk@microsoft.com", "ericwilligers@google.com" ],
+    "expiry_milestone": 89
+  },
   {
     "name": "webpage-default-zoom-from-dynamic-type",
     "owners": [ "rkgibson", "bling-flags" ],

chrome/browser/flag_descriptions.cc

@@ -4459,6 +4459,13 @@ const char kUserDataSnapshotDescription[] =
     "update and restoring them after a version rollback.";
 #endif  // !defined(OS_ANDROID) && !defined(OS_CHROMEOS)
 
+#if defined(OS_WIN) || defined(OS_CHROMEOS)
+const char kWebShareName[] = "Web Share";
+const char kWebShareDescription[] =
+    "Enables the Web Share (navigator.share) APIs on experimentally supported "
+    "platforms.";
+#endif  // defined(OS_WIN) || defined(OS_CHROMEOS)
+
 // Feature flags --------------------------------------------------------------
 
 #if defined(DCHECK_IS_CONFIGURABLE)

chrome/browser/flag_descriptions.h

@@ -2617,6 +2617,11 @@ extern const char kUserDataSnapshotName[];
 extern const char kUserDataSnapshotDescription[];
 #endif  // !defined(OS_ANDROID) && !defined(OS_CHROMEOS)
 
+#if defined(OS_WIN) || defined(OS_CHROMEOS)
+extern const char kWebShareName[];
+extern const char kWebShareDescription[];
+#endif  // defined(OS_WIN) || defined(OS_CHROMEOS)
+
 // Feature flags --------------------------------------------------------------
 
 #if defined(DCHECK_IS_CONFIGURABLE)

chrome/common/chrome_features.cc

@@ -812,6 +812,11 @@ const base::Feature kWebRtcRemoteEventLogGzipped{
     "WebRtcRemoteEventLogGzipped", base::FEATURE_ENABLED_BY_DEFAULT};
 #endif
 
+#if defined(OS_WIN) || defined(OS_CHROMEOS)
+// Enables Web Share (navigator.share)
+const base::Feature kWebShare{"WebShare", base::FEATURE_DISABLED_BY_DEFAULT};
+#endif
+
 // Enables setting time limit for Chrome and PWA's on child user device.
 // Requires |kPerAppTimeLimits| to be enabled.
 #if defined(OS_CHROMEOS)

chrome/common/chrome_features.h

@@ -552,6 +552,10 @@ COMPONENT_EXPORT(CHROME_FEATURES)
 extern const base::Feature kWebRtcRemoteEventLogGzipped;
 #endif
 
+#if defined(OS_WIN) || defined(OS_CHROMEOS)
+COMPONENT_EXPORT(CHROME_FEATURES) extern const base::Feature kWebShare;
+#endif
+
 #if defined(OS_CHROMEOS)
 COMPONENT_EXPORT(CHROME_FEATURES)
 extern const base::Feature kWebTimeLimits;

chrome/renderer/chrome_content_renderer_client.cc

@@ -1490,11 +1490,14 @@ void ChromeContentRendererClient::
   // embedder only.
   blink::WebRuntimeFeatures::EnablePerformanceManagerInstrumentation(true);
 
-// Web Share is shipped on Android, experimental otherwise. It is enabled here,
-// in chrome/, to avoid it being made available in other clients of content/
-// that do not have a Web Share Mojo implementation.
-#if defined(OS_ANDROID)
-  blink::WebRuntimeFeatures::EnableWebShare(true);
+  // Web Share is conditionally enabled here in chrome/, to avoid it being
+  // made available in other clients of content/ that do not have a Web Share
+  // Mojo implementation (e.g. WebView).  Web Share is shipped on Android.
+#if defined(OS_CHROMEOS) || defined(OS_WIN)
+  if (base::FeatureList::IsEnabled(features::kWebShare))
+#endif
+#if defined(OS_CHROMEOS) || defined(OS_WIN) || defined(OS_ANDROID)
+    blink::WebRuntimeFeatures::EnableWebShare(true);
 #endif
 
   if (base::FeatureList::IsEnabled(subresource_filter::kAdTagging))

tools/metrics/histograms/enums.xml

@@ -40207,6 +40207,7 @@ from previous Chrome versions.
   <int value="-1938263248" label="enable-extension-info-dialog"/>
   <int value="-1937077699" label="http-form-warning"/>
   <int value="-1936032607" label="enable-experimental-webassembly-features"/>
+  <int value="-1935055754" label="WebShare:enabled"/>
   <int value="-1934661084" label="ForceUnifiedConsentBump:disabled"/>
   <int value="-1933425042" label="OfflinePreviews:enabled"/>
   <int value="-1932609987" label="CSSBackdropFilter:disabled"/>
@@ -41788,6 +41789,7 @@ from previous Chrome versions.
   <int value="-311148335" label="v8-pac-mojo-out-of-process"/>
   <int value="-310908854" label="new-wallpaper-picker"/>
   <int value="-310615515" label="EnableSuggestedFiles:disabled"/>
+  <int value="-308793293" label="WebShare:disabled"/>
   <int value="-307260007" label="ExtensionsCheckup:disabled"/>
   <int value="-306935714" label="lite-video-force-override-decision"/>
   <int value="-304951461" label="TextSuggestionsTouchBar:enabled"/>