Add a JS API for detecting WebGL availability.

chrome/browser/extensions/extension_webstore_private_api.cc

Index: chrome/browser/extensions/extension_webstore_private_api.cc
===================================================================
--- chrome/browser/extensions/extension_webstore_private_api.cc	(revision 112998)
+++ chrome/browser/extensions/extension_webstore_private_api.cc	(working copy)
@@ -491,3 +491,63 @@
   prefs->SetWebStoreLogin(login);
   return true;
 }
+
+GetWebGLStatusFunction::GetWebGLStatusFunction() {}
+GetWebGLStatusFunction::~GetWebGLStatusFunction() {}
+
+// static
+bool GetWebGLStatusFunction::IsWebGLAllowed(GpuDataManager* manager) {
+  bool webgl_allowed = true;
+  if (!manager->GpuAccessAllowed()) {
+    webgl_allowed = false;
+  } else {
+    uint32 blacklist_flags = manager->GetGpuFeatureFlags().flags();
+    if (blacklist_flags & GpuFeatureFlags::kGpuFeatureWebgl)
+      webgl_allowed = false;
+  }
+  return webgl_allowed;
+}
+
+void GetWebGLStatusFunction::OnGpuInfoUpdate() {
+  GpuDataManager* manager = GpuDataManager::GetInstance();
+  manager->RemoveObserver(this);
+  bool webgl_allowed = IsWebGLAllowed(manager);
+  CreateResult(webgl_allowed);
+  SendResponse(true);
+
+  // Matches the AddRef in RunImpl().
+  Release();
+}
+
+void GetWebGLStatusFunction::CreateResult(bool webgl_allowed) {
+  result_.reset(Value::CreateStringValue(
+      webgl_allowed ? "webgl_allowed" : "webgl_blocked"));
+}
+
+bool GetWebGLStatusFunction::RunImpl() {
+  bool finalized = true;
+#if defined(OS_LINUX)

[Mihai Parparita -not on Chrome, 2011/12/07 00:01:38]

Can you comment why Linux gets this special treatment? Better yet, can this
knowledge be in GpuDataManager (i.e. should complete_gpu_info_available always
return true on Mac and Windows?) 

[Zhenyao Mo, 2011/12/07 17:26:51]

On Mac/Windows, gpu info is also incomplete without gpu process launching.  Only
that so far the partial information is always enough to make the final blacklist
decision.  So it's rather a hack here to speed up this GetWebGLStatusFunction in
Mac and Win.  I feel it's better to just add a comment to explain the situation
here.

+  finalized = false;
+#endif
+
+  GpuDataManager* manager = GpuDataManager::GetInstance();
+  if (manager->complete_gpu_info_available())
+    finalized = true;
+
+  bool webgl_allowed = IsWebGLAllowed(manager);
+  if (!webgl_allowed)
+    finalized = true;
+
+  if (finalized) {
+    CreateResult(webgl_allowed);
+    SendResponse(true);
+  } else {
+    // Matched with a Release in OnGpuInfoUpdate.
+    AddRef();
+
+    manager->AddObserver(this);
+    manager->RequestCompleteGpuInfoIfNeeded();
+  }
+  return true;
+}
+