Fix data race in InspectorInstrumentation::hasFrontends

BUG=527736

Review URL: https://codereview.chromium.org/1301323008

git-svn-id: svn://svn.chromium.org/blink/trunk@201750 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/inspector/InspectorInstrumentation.h

@@ -92,7 +92,7 @@ private:
 
 inline void frontendCreated() { atomicIncrement(&FrontendCounter::s_frontendCounter); }
 inline void frontendDeleted() { atomicDecrement(&FrontendCounter::s_frontendCounter); }
-inline bool hasFrontends() { return FrontendCounter::s_frontendCounter; }
+inline bool hasFrontends() { return acquireLoad(&FrontendCounter::s_frontendCounter); }
 
 CORE_EXPORT void registerInstrumentingAgents(InstrumentingAgents*);
 CORE_EXPORT void unregisterInstrumentingAgents(InstrumentingAgents*);