Add a JS API for detecting WebGL availability.

chrome/browser/extensions/extension_webstore_private_api.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/extensions/extension_webstore_private_api.h"
 
 #include <string>
 
 #include "base/string_util.h"
 #include "base/utf_string_conversions.h"
@@ skipping 473 matching lines @@
 bool SetStoreLoginFunction::RunImpl() {
   if (!IsWebStoreURL(profile_, source_url()))
     return false;
   std::string login;
   EXTENSION_FUNCTION_VALIDATE(args_->GetString(0, &login));
   ExtensionService* service = profile_->GetExtensionService();
   ExtensionPrefs* prefs = service->extension_prefs();
   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);
+  result_.reset(Value::CreateStringValue(
+      webgl_allowed ? "webgl_allowed" : "webgl_blocked"));
+  SendResponse(true);
+
+  Release();
+}
+
+bool GetWebGLStatusFunction::RunImpl() {
+  bool finalized = true;
+#if defined(OS_LINUX)
+  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) {
+    result_.reset(Value::CreateStringValue(
+        webgl_allowed ? "webgl_allowed" : "webgl_blocked"));
+    SendResponse(true);
+  } else {
+    manager->AddObserver(this);

[Ken Russell (switch to Gerrit), 2011/12/03 02:59:42]

I don't fully understand the multithreading in this code, but is it possible for
the full GPU information to become available between the time that
complete_gpu_info_available() is called above, and when AddObserver is called
here? If so, then is it possible the observer will never be called because it is
added after the event occurs of the full GPU info becoming available?

[Zhenyao Mo, 2011/12/03 07:13:27]

Ah you are right.  I need to think more on this.

+    manager->RequestCompleteGpuInfoIfNeeded();
+
+    AddRef();
+  }
+  return true;
+}
+