Make CommandBuffer::Flush asynchronous, and add CommandBuffer::FlushSync with former semantics.

gpu/command_buffer/client/cmd_buffer_helper.cc

Index: gpu/command_buffer/client/cmd_buffer_helper.cc
diff --git a/gpu/command_buffer/client/cmd_buffer_helper.cc b/gpu/command_buffer/client/cmd_buffer_helper.cc
index b666e83dc5dc18134cbe8acfdd677ae5fdde7df6..b714622313e50bc0b3138b95e9153c8ea84d7c0b 100644
--- a/gpu/command_buffer/client/cmd_buffer_helper.cc
+++ b/gpu/command_buffer/client/cmd_buffer_helper.cc
@@ -45,19 +45,23 @@ bool CommandBufferHelper::Initialize(int32 ring_buffer_size) {
 CommandBufferHelper::~CommandBufferHelper() {
 }
 
-bool CommandBufferHelper::Flush() {
-  CommandBuffer::State state = command_buffer_->Flush(put_);
+bool CommandBufferHelper::FlushSync() {
+  CommandBuffer::State state = command_buffer_->FlushSync(put_);
   SynchronizeState(state);
   return state.error == error::kNoError;
 }
 
+void CommandBufferHelper::Flush() {
+  command_buffer_->Flush(put_);
+}
+
 // Calls Flush() and then waits until the buffer is empty. Break early if the
 // error is set.
 bool CommandBufferHelper::Finish() {
   do {
     // Do not loop forever if the flush fails, meaning the command buffer reader
     // has shutdown.
-    if (!Flush())
+    if (!FlushSync())
       return false;
   } while (put_ != get_);
 
@@ -98,7 +102,7 @@ void CommandBufferHelper::WaitForToken(int32 token) {
     }
     // Do not loop forever if the flush fails, meaning the command buffer reader
     // has shutdown.
-    if (!Flush())
+    if (!FlushSync())
       return;
   }
 }
@@ -120,7 +124,7 @@ void CommandBufferHelper::WaitForAvailableEntries(int32 count) {
     while (get_ > put_ || get_ == 0) {
       // Do not loop forever if the flush fails, meaning the command buffer
       // reader has shutdown.
-      if (!Flush())
+      if (!FlushSync())
         return;
     }
     // Insert a jump back to the beginning.
@@ -134,7 +138,7 @@ void CommandBufferHelper::WaitForAvailableEntries(int32 count) {
   while (AvailableEntries() < count) {
     // Do not loop forever if the flush fails, meaning the command buffer reader
     // has shutdown.
-    if (!Flush())
+    if (!FlushSync())
       return;
   }
 }