Fix race conditions in window snapshot code.

content/renderer/render_thread_impl.cc

Index: content/renderer/render_thread_impl.cc
diff --git a/content/renderer/render_thread_impl.cc b/content/renderer/render_thread_impl.cc
index bc5f6792f32b1e57d869ad1777f09c305ce7a35b..1eb2c21b30f359942a3c978910c5ca00c8cf4d03 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -398,6 +398,8 @@ void RenderThreadImpl::Init() {
   memory_pressure_listener_.reset(new base::MemoryPressureListener(
       base::Bind(&RenderThreadImpl::OnMemoryPressure, base::Unretained(this))));
 
+  renderer_process_id_ = base::kNullProcessId;
+
   TRACE_EVENT_END_ETW("RenderThreadImpl::Init", 0, "");
 }
 
@@ -1094,6 +1096,7 @@ bool RenderThreadImpl::OnControlMessageReceived(const IPC::Message& msg) {
     IPC_MESSAGE_HANDLER(ViewMsg_PurgePluginListCache, OnPurgePluginListCache)
     IPC_MESSAGE_HANDLER(ViewMsg_NetworkStateChanged, OnNetworkStateChanged)
     IPC_MESSAGE_HANDLER(ViewMsg_TempCrashWithData, OnTempCrashWithData)
+    IPC_MESSAGE_HANDLER(ViewMsg_SetRendererProcessID, OnSetRendererProcessID)
     IPC_MESSAGE_HANDLER(ViewMsg_SetWebKitSharedTimersSuspended,
                         OnSetWebKitSharedTimersSuspended)
     IPC_MESSAGE_UNHANDLED(handled = false)
@@ -1231,6 +1234,10 @@ void RenderThreadImpl::OnTempCrashWithData(const GURL& data) {
   CHECK(false);
 }
 
+void RenderThreadImpl::OnSetRendererProcessID(base::ProcessId process_id) {
+  renderer_process_id_ = process_id;
+}
+
 void RenderThreadImpl::OnSetWebKitSharedTimersSuspended(bool suspend) {
   ToggleWebKitSharedTimer(suspend);
 }
@@ -1295,4 +1302,8 @@ void RenderThreadImpl::SampleGamepads(WebKit::WebGamepads* data) {
   gamepad_shared_memory_reader_->SampleGamepads(*data);
 }
 
+base::ProcessId RenderThreadImpl::renderer_process_id() const {
+  return renderer_process_id_;
+}
+
 }  // namespace content