content: Fix Context creation logic in ContextProviderFactoryImpl.

ui/android/context_provider_factory.h

Index: ui/android/context_provider_factory.h
diff --git a/ui/android/context_provider_factory.h b/ui/android/context_provider_factory.h
index 8ad9d6f4a0c3eacef8a1e0982a974b337ceb4684..c5654d768840c2389d88ca56fb064b9379d13ba4 100644
--- a/ui/android/context_provider_factory.h
+++ b/ui/android/context_provider_factory.h
@@ -31,8 +31,24 @@ namespace ui {
 // This class is not thread-safe and should only be accessed from the UI thread.
 class UI_ANDROID_EXPORT ContextProviderFactory {
  public:
+  enum class ContextCreationResult {
+    FAILURE_GPU_PROCESS_INITIALIZATION_FAILED,
+
+    // Used when the browser is shutting down. No more requests should be made

[David Trainor- moved to gerrit, 2016/08/18 17:49:43]

Should we enforce/DCHECK that we don't get calls after sending this?

[Khushal, 2016/08/18 18:29:13]

We can internally enforce that we are not getting any callbacks while we are
running the existing ones with a shutdown response. Should we also add a
DidShutdown() method to the factory that the caller should check before making a
request?

+    // after this.
+    FAILURE_BROWSER_SHUTDOWN,
+
+    // The GpuSurfaceHandle for the request was lost before the context could be
+    // created. This is used for on-screen context requests only.
+    FAILURE_GPU_SURFACE_HANDLE_LOST,
+
+    // Set if the Context creation was successful.
+    SUCCESS,
+  };
+
   using ContextProviderCallback =
-      base::Callback<void(const scoped_refptr<cc::ContextProvider>&)>;
+      base::Callback<void(const scoped_refptr<cc::ContextProvider>&,
+                          ContextCreationResult)>;
 
   enum class ContextType {
     BLIMP_RENDER_COMPOSITOR_CONTEXT,
@@ -52,8 +68,8 @@ class UI_ANDROID_EXPORT ContextProviderFactory {
 
   // Creates an offscreen ContextProvider for the compositor. Any shared
   // contexts passed here *must* have been created using this factory.
-  // The callback may be triggered synchronously if possible, and will always
-  // have the context provider.
+  // The callback may be triggered synchronously if possible. If the context
+  // creation fails, a null context is passed with the specified reason.
   virtual void CreateOffscreenContextProvider(
       ContextType context_type,
       gpu::SharedMemoryLimits shared_memory_limits,