Re-land of http://codereview.chromium.org/6094009 with Mac build fix....

chrome/browser/gpu_process_host.cc

 // Copyright (c) 2010 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/gpu_process_host.h"
 
 #include "app/app_switches.h"
 #include "app/resource_bundle.h"
 #include "base/command_line.h"
 #include "base/metrics/histogram.h"
@@ skipping 79 matching lines @@
     queued_synchronization_replies_.pop();
   }
   DCHECK_EQ(sole_instance_, this);
   sole_instance_ = NULL;
 }
 
 bool GpuProcessHost::EnsureInitialized() {
   if (!initialized_) {
     initialized_ = true;
     initialized_successfully_ = Init();
+    if (initialized_successfully_) {
+      Send(new GpuMsg_Initialize());
+    }
   }
   return initialized_successfully_;
 }
 
 bool GpuProcessHost::Init() {
   if (!LoadGpuBlacklist())
     return false;
 
   if (!CreateChannel())
     return false;
@@ skipping 111 matching lines @@
   if (gpu_feature_flags.flags() != 0) {
     Send(new GpuMsg_CloseChannel(channel_handle));
     SendEstablishChannelReply(IPC::ChannelHandle(), gpu_info, request.filter);
   } else {
     SendEstablishChannelReply(channel_handle, gpu_info, request.filter);
   }
   sent_requests_.pop();
 }
 
 void GpuProcessHost::OnSynchronizeReply() {
-  const SynchronizationRequest& request =
-      queued_synchronization_replies_.front();
-  SendSynchronizationReply(request.reply, request.filter);
-  queued_synchronization_replies_.pop();
+  // Guard against race conditions in abrupt GPU process termination.
+  if (queued_synchronization_replies_.size() > 0) {
+    const SynchronizationRequest& request =
+        queued_synchronization_replies_.front();
+    SendSynchronizationReply(request.reply, request.filter);
+    queued_synchronization_replies_.pop();
+  }
 }
 
 #if defined(OS_LINUX)
 
 namespace {
 
 void SendDelayedReply(IPC::Message* reply_msg) {
   GpuProcessHost::Get()->Send(reply_msg);
 }
 
@@ skipping 228 matching lines @@
   filter->Send(message);
 }
 
 // Sends the response for synchronization request to the renderer.
 void GpuProcessHost::SendSynchronizationReply(
     IPC::Message* reply,
     RenderMessageFilter* filter) {
   filter->Send(reply);
 }
 
+void GpuProcessHost::SendOutstandingReplies() {
+  // First send empty channel handles for all EstablishChannel requests.
+  while (!sent_requests_.empty()) {
+    const ChannelRequest& request = sent_requests_.front();
+    SendEstablishChannelReply(IPC::ChannelHandle(), GPUInfo(), request.filter);
+    sent_requests_.pop();
+  }
+
+  // Now unblock all renderers waiting for synchronization replies.
+  while (!queued_synchronization_replies_.empty()) {
+    OnSynchronizeReply();
+  }
+}
+
 bool GpuProcessHost::CanShutdown() {
   return true;
 }
 
 void GpuProcessHost::OnChildDied() {
+  SendOutstandingReplies();
   // Located in OnChildDied because OnProcessCrashed suffers from a race
   // condition on Linux. The GPU process will only die if it crashes.
   UMA_HISTOGRAM_ENUMERATION("GPU.GPUProcessLifetimeEvents",
                             kCrashed, kGPUProcessLifetimeEvent_Max);
   BrowserChildProcessHost::OnChildDied();
 }
 
 void GpuProcessHost::OnProcessCrashed(int exit_code) {
+  SendOutstandingReplies();
   if (++g_gpu_crash_count >= kGpuMaxCrashCount) {
     // The gpu process is too unstable to use. Disable it for current session.
     RenderViewHostDelegateHelper::set_gpu_enabled(false);
   }
   BrowserChildProcessHost::OnProcessCrashed(exit_code);
 }
 
 bool GpuProcessHost::CanLaunchGpuProcess() const {
   return RenderViewHostDelegateHelper::gpu_enabled();
 }
@@ skipping 58 matching lines @@
   const CommandLine& browser_command_line = *CommandLine::ForCurrentProcess();
   if (browser_command_line.HasSwitch(switches::kIgnoreGpuBlacklist) ||
       blacklist->LoadGpuBlacklist(gpu_blacklist_json.as_string(), true)) {
     gpu_blacklist_.reset(blacklist);
     return true;
   }
   delete blacklist;
   return false;
 }