Lock-free GamepadSeqLock (try 2)

content/browser/gamepad/gamepad_provider.cc

Index: content/browser/gamepad/gamepad_provider.cc
===================================================================
--- content/browser/gamepad/gamepad_provider.cc	(revision 145136)
+++ content/browser/gamepad/gamepad_provider.cc	(working copy)
@@ -121,11 +121,6 @@
   bool changed;
   GamepadHardwareBuffer* hwbuf = SharedMemoryAsHardwareBuffer();
 
-  ANNOTATE_BENIGN_RACE_SIZED(
-      &hwbuf->buffer,
-      sizeof(WebKit::WebGamepads),
-      "Racey reads are discarded");
-
   {
     base::AutoLock lock(devices_changed_lock_);
     changed = devices_changed_;
@@ -134,9 +129,9 @@
 
   // Acquire the SeqLock. There is only ever one writer to this data.
   // See gamepad_hardware_buffer.h.
-  hwbuf->sequence.WriteBegin();
-  data_fetcher_->GetGamepadData(&hwbuf->buffer, changed);
-  hwbuf->sequence.WriteEnd();
+  WebKit::WebGamepads tmp;
+  data_fetcher_->GetGamepadData(&tmp, changed);
+  hwbuf->gamepads.Write(tmp);
 
   // Schedule our next interval of polling.
   ScheduleDoPoll();