Bug 1398393 - Set Servo thread state on cooperative threads. r=billm

By doing this we avoid triggering assertions in the Servo code that ensure
we have registered the thread with Servo and set the proper state on it.

MozReview-Commit-ID: K6qHrYoQDLm

--HG--
extra : rebase_source : d01b0aad42273f6b92b7cfd5f5fe17ffe7b4cda0

layout/style/ServoBindingList.h

@@ -549,6 +549,8 @@ SERVO_BINDING_FUNC(Servo_ComputedValues_GetStyleRuleList, void,
 // Initialize Servo components. Should be called exactly once at startup.
 SERVO_BINDING_FUNC(Servo_Initialize, void,
                    RawGeckoURLExtraData* dummy_url_data)
+// Initialize Servo on a cooperative Quantum DOM thread.
+SERVO_BINDING_FUNC(Servo_InitializeCooperativeThread, void);
 // Shut down Servo components. Should be called exactly once at shutdown.
 SERVO_BINDING_FUNC(Servo_Shutdown, void)
 

xpcom/threads/CooperativeThreadPool.cpp

@@ -8,6 +8,7 @@
 
 #include "base/message_loop.h"
 #include "mozilla/IOInterposer.h"
+#include "mozilla/ServoBindings.h"
 #include "nsError.h"
 #include "nsThreadUtils.h"
 

xpcom/threads/Scheduler.cpp

@@ -653,6 +653,7 @@ SchedulerImpl::ThreadController::OnStartThread(size_t aIndex, const nsACString&
     JS_AddInterruptCallback(cx, SchedulerImpl::InterruptCallback);
   }
   js::SetCooperativeYieldCallback(cx, SchedulerImpl::YieldCallback);
+  Servo_InitializeCooperativeThread();
 }
 
 void