aw: Prevent multiple AddObserver

content/renderer/media/android/stream_texture_factory_synchronous_impl.cc

Index: content/renderer/media/android/stream_texture_factory_synchronous_impl.cc
diff --git a/content/renderer/media/android/stream_texture_factory_synchronous_impl.cc b/content/renderer/media/android/stream_texture_factory_synchronous_impl.cc
index e46395d0cd1de7a1a380dbe88147be471fba60a6..093012a150750aef59e9cc591d0dff6550b99ce6 100644
--- a/content/renderer/media/android/stream_texture_factory_synchronous_impl.cc
+++ b/content/renderer/media/android/stream_texture_factory_synchronous_impl.cc
@@ -166,13 +166,14 @@ StreamTextureFactorySynchronousImpl::StreamTextureFactorySynchronousImpl(
 StreamTextureFactorySynchronousImpl::~StreamTextureFactorySynchronousImpl() {}
 
 StreamTextureProxy* StreamTextureFactorySynchronousImpl::CreateProxy() {
-  if (!context_provider_)
+  bool had_proxy = !!context_provider_;
+  if (!had_proxy)
     context_provider_ = create_context_provider_callback_.Run();
 
   if (!context_provider_)
     return NULL;
 
-  if (observer_)
+  if (observer_ && !had_proxy)
     context_provider_->AddObserver(observer_);
   return new StreamTextureProxyImpl(context_provider_);
 }