gpu: Fix some context lost marking glitches+leaks and add UMA stats

content/common/gpu/gpu_command_buffer_stub.cc

Index: content/common/gpu/gpu_command_buffer_stub.cc
diff --git a/content/common/gpu/gpu_command_buffer_stub.cc b/content/common/gpu/gpu_command_buffer_stub.cc
index e14cf986092b9c8817dcd3024e2474890734c368..ecb99048ce18776caa1ef4c8f4f70e0a85b7b8f2 100644
--- a/content/common/gpu/gpu_command_buffer_stub.cc
+++ b/content/common/gpu/gpu_command_buffer_stub.cc
@@ -421,9 +421,11 @@ void GpuCommandBufferStub::Destroy() {
   scheduler_.reset();
 
   bool have_context = false;
-  if (decoder_ && command_buffer_ &&
-      command_buffer_->GetLastState().error != gpu::error::kLostContext)
-    have_context = decoder_->MakeCurrent();
+  if (decoder_) {
+    // Try to make the context current regardless of whether it was lost, so we
+    // don't leak resources.

[Ken Russell (switch to Gerrit), 2015/04/27 22:35:33]

Presumably if the driver has actually lost the context then the resources have
all been invalidated / reclaimed. This change seems OK though.

[no sievers, 2015/04/27 23:24:41]

But it's a problem if we forced the context to be lost for GL_OUT_OF_MEMORY or
something else.

+    have_context = decoder_->GetGLContext()->MakeCurrent(surface_.get());
+  }
   FOR_EACH_OBSERVER(DestructionObserver,
                     destruction_observers_,
                     OnWillDestroyStub());
@@ -671,7 +673,7 @@ void GpuCommandBufferStub::OnParseError() {
   DCHECK(command_buffer_.get());
   gpu::CommandBuffer::State state = command_buffer_->GetLastState();
   IPC::Message* msg = new GpuCommandBufferMsg_Destroyed(
-      route_id_, state.context_lost_reason);
+      route_id_, state.context_lost_reason, state.error);
   msg->set_unblock(true);
   Send(msg);
 
@@ -1089,7 +1091,7 @@ void GpuCommandBufferStub::MarkContextLost() {
 
   command_buffer_->SetContextLostReason(gpu::error::kUnknown);
   if (decoder_)
-    decoder_->LoseContext(GL_UNKNOWN_CONTEXT_RESET_ARB);
+    decoder_->MarkContextLost(gpu::error::kUnknown);
   command_buffer_->SetParseError(gpu::error::kLostContext);
 }