Bug 1330184 - Register/unregister the IOInterposeObserver on the main thread, regardless of what thread the profiler is started / stopped on. r=njn

MozReview-Commit-ID: 8Y0rspxBJw3

--HG--
extra : rebase_source : a3fff1f5d94f7071200b7adc7010c11a1198661f
extra : source : fd537bffda4b653dc7191434c42d068b1b9c65b8

tools/profiler/core/platform.cpp

@@ -298,16 +298,32 @@ private:
     }
 
     if (mInterposeObserver) {
-      mozilla::IOInterposer::Register(mozilla::IOInterposeObserver::OpAll,
-                                      mInterposeObserver.get());
+      // We need to register the observer on the main thread, because we want
+      // to observe IO that happens on the main thread.
+      if (NS_IsMainThread()) {
+        IOInterposer::Register(IOInterposeObserver::OpAll, mInterposeObserver);
+      } else {
+        RefPtr<ProfilerIOInterposeObserver> observer = mInterposeObserver;
+        NS_DispatchToMainThread(NS_NewRunnableFunction([=]() {
+          IOInterposer::Register(IOInterposeObserver::OpAll, observer);
+        }));
+      }
     }
   }
 
   ~ActivePS()
   {
     if (mInterposeObserver) {
-      mozilla::IOInterposer::Unregister(mozilla::IOInterposeObserver::OpAll,
-                                        mInterposeObserver.get());
+      // We need to unregister the observer on the main thread, because that's
+      // where we've registered it.
+      if (NS_IsMainThread()) {
+        IOInterposer::Unregister(IOInterposeObserver::OpAll, mInterposeObserver);
+      } else {
+        RefPtr<ProfilerIOInterposeObserver> observer = mInterposeObserver;
+        NS_DispatchToMainThread(NS_NewRunnableFunction([=]() {
+          IOInterposer::Unregister(IOInterposeObserver::OpAll, observer);
+        }));
+      }
     }
   }
 
@@ -450,7 +466,7 @@ private:
   SamplerThread* const mSamplerThread;
 
   // The interposer that records main thread I/O.
-  const UniquePtr<mozilla::ProfilerIOInterposeObserver> mInterposeObserver;
+  const RefPtr<mozilla::ProfilerIOInterposeObserver> mInterposeObserver;
 
   // Is the profiler paused?
   bool mIsPaused;

tools/profiler/gecko/ProfilerIOInterposeObserver.h

@@ -8,6 +8,7 @@
 #ifdef MOZ_GECKO_PROFILER
 
 #include "mozilla/IOInterposer.h"
+#include "nsISupportsImpl.h"
 
 namespace mozilla {
 
@@ -17,8 +18,13 @@ namespace mozilla {
  */
 class ProfilerIOInterposeObserver final : public IOInterposeObserver
 {
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(ProfilerIOInterposeObserver)
+
 public:
   virtual void Observe(Observation& aObservation);
+
+protected:
+  virtual ~ProfilerIOInterposeObserver() {}
 };
 
 } // namespace mozilla