Revert of Hold the Pepper proxy lock for all Pepper GL calls. (patchset #3...

Revert of Hold the Pepper proxy lock for all Pepper GL calls. (patchset #3 id:40001 of https://codereview.chromium.org/692683003/)

Reason for revert:
causing huge crashes in canary. bug=429446

Original issue's description:
> Hold the Pepper proxy lock for all Pepper GL calls.
>
> BUG=418651
>
> Committed: https://crrev.com/057f7a69dd40c93550b375b4287dba70d719316a
> Cr-Commit-Position: refs/heads/master@{#302303}

TBR=dmichael@chromium.org,dmichael@google.com,penghuang@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=418651

Review URL: https://codereview.chromium.org/698463006

Cr-Commit-Position: refs/heads/master@{#302391}

ppapi/proxy/plugin_dispatcher.cc

@@ -211,15 +211,6 @@ bool PluginDispatcher::Send(IPC::Message* msg) {
   return SendMessage(msg);
 }
 
-bool PluginDispatcher::SendAndStayLocked(IPC::Message* msg) {
-  TRACE_EVENT2("ppapi proxy", "PluginDispatcher::SendAndStayLocked",
-               "Class", IPC_MESSAGE_ID_CLASS(msg->type()),
-               "Line", IPC_MESSAGE_ID_LINE(msg->type()));
-  if (!msg->is_reply())
-    msg->set_unblock(true);
-  return SendMessage(msg);
-}
-
 bool PluginDispatcher::OnMessageReceived(const IPC::Message& msg) {
   // We need to grab the proxy lock to ensure that we don't collide with the
   // plugin making pepper calls on a different thread.

ppapi/proxy/plugin_dispatcher.h

@@ -140,15 +140,12 @@ class PPAPI_PROXY_EXPORT PluginDispatcher
                              bool is_client);
 
   // Dispatcher overrides.
-  bool IsPlugin() const override;
-  bool Send(IPC::Message* msg) override;
-  // Unlike |Send()|, this function continues to hold the Pepper proxy lock
-  // unconditionally.
-  bool SendAndStayLocked(IPC::Message* msg) override;
+  virtual bool IsPlugin() const;
+  virtual bool Send(IPC::Message* msg);
 
   // IPC::Listener implementation.
-  bool OnMessageReceived(const IPC::Message& msg) override;
-  void OnChannelError() override;
+  virtual bool OnMessageReceived(const IPC::Message& msg);
+  virtual void OnChannelError();
 
   // Keeps track of which dispatcher to use for each instance, active instances
   // and tracks associated data like the current size.

ppapi/proxy/ppapi_command_buffer_proxy.cc

@@ -219,10 +219,7 @@ int32 PpapiCommandBufferProxy::CreateGpuMemoryBufferImage(
 bool PpapiCommandBufferProxy::Send(IPC::Message* msg) {
   DCHECK(last_state_.error == gpu::error::kNoError);
 
-  // We need hold the Pepper proxy lock for sync IPC, because GPU command buffer
-  // may use a sync IPC with another lock held. It may cause deadlock.
-  // http://crbug.com/418651
-  if (channel_->SendAndStayLocked(msg))
+  if (channel_->Send(msg))
     return true;
 
   last_state_.error = gpu::error::kLostContext;

ppapi/proxy/proxy_channel.cc

@@ -85,9 +85,5 @@ bool ProxyChannel::Send(IPC::Message* msg) {
   return false;
 }
 
-bool ProxyChannel::SendAndStayLocked(IPC::Message* msg) {
-  return Send(msg);
-}
-
 }  // namespace proxy
 }  // namespace ppapi

ppapi/proxy/proxy_channel.h

@@ -73,8 +73,6 @@ class PPAPI_PROXY_EXPORT ProxyChannel
   // IPC::Sender implementation.
   virtual bool Send(IPC::Message* msg) override;
 
-  virtual bool SendAndStayLocked(IPC::Message* msg);
-
   // IPC::Listener implementation.
   virtual void OnChannelError() override;