--- a/dom/media/platforms/wmf/WMFDecoderModule.cpp
+++ b/dom/media/platforms/wmf/WMFDecoderModule.cpp
@@ -22,17 +22,17 @@
 #include "MediaInfo.h"
 #include "MediaPrefs.h"
 #include "prsystem.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/StaticMutex.h"
 
 namespace mozilla {
 
-static bool sDXVAEnabled = false;
+static Atomic<bool> sDXVAEnabled(false);
 
 WMFDecoderModule::WMFDecoderModule()
   : mWMFInitialized(false)
 {
 }
 
 WMFDecoderModule::~WMFDecoderModule()
 {
@@ -41,17 +41,16 @@ WMFDecoderModule::~WMFDecoderModule()
     NS_ASSERTION(SUCCEEDED(hr), "MFShutdown failed");
   }
 }
 
 /* static */
 void
 WMFDecoderModule::Init()
 {
-  MOZ_ASSERT(NS_IsMainThread(), "Must be on main thread.");
   sDXVAEnabled = gfxPlatform::GetPlatform()->CanUseHardwareVideoDecoding();
 }
 
 /* static */
 int
 WMFDecoderModule::GetNumDecoderThreads()
 {
   int32_t numCores = PR_GetNumberOfProcessors();

--- a/gfx/thebes/gfxPlatform.cpp
+++ b/gfx/thebes/gfxPlatform.cpp
@@ -123,16 +123,17 @@ static const uint32_t kDefaultGlyphCache
 
 #if !defined(USE_SKIA) || !defined(USE_SKIA_GPU)
 class mozilla::gl::SkiaGLGlue : public GenericAtomicRefCounted {
 };
 #endif
 
 #include "mozilla/Preferences.h"
 #include "mozilla/Assertions.h"
+#include "mozilla/Atomics.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/Mutex.h"
 
 #include "nsAlgorithm.h"
 #include "nsIGfxInfo.h"
 #include "nsIXULRuntime.h"
 #include "VsyncSource.h"
 #include "SoftwareVsyncSource.h"
@@ -2057,22 +2058,22 @@ gfxPlatform::OptimalFormatForContent(gfx
 /**
  * There are a number of layers acceleration (or layers in general) preferences
  * that should be consistent for the lifetime of the application (bug 840967).
  * As such, we will evaluate them all as soon as one of them is evaluated
  * and remember the values.  Changing these preferences during the run will
  * not have any effect until we restart.
  */
 bool gANGLESupportsD3D11 = false;
-static bool sLayersSupportsHardwareVideoDecoding = false;
+static mozilla::Atomic<bool> sLayersSupportsHardwareVideoDecoding(false);
 static bool sLayersHardwareVideoDecodingFailed = false;
 static bool sBufferRotationCheckPref = true;
 static bool sPrefBrowserTabsRemoteAutostart = false;
 
-static bool sLayersAccelerationPrefsInitialized = false;
+static mozilla::Atomic<bool> sLayersAccelerationPrefsInitialized(false);
 
 void
 gfxPlatform::InitAcceleration()
 {
   if (sLayersAccelerationPrefsInitialized) {
     return;
   }
 

--- a/gfx/thebes/gfxWindowsPlatform.h
+++ b/gfx/thebes/gfxWindowsPlatform.h
@@ -222,17 +222,17 @@ public:
       HRESULT& aResOut);
 
     bool DwmCompositionEnabled();
 
     mozilla::layers::ReadbackManagerD3D11* GetReadbackManager();
 
     static bool IsOptimus();
 
-    bool IsWARP() { return mIsWARP; }
+    bool IsWARP() const { return mIsWARP; }
 
     // Returns whether the compositor's D3D11 device supports texture sharing.
     bool CompositorD3D11TextureSharingWorks() const {
       return mCompositorD3D11TextureSharingWorks;
     }
 
     bool SupportsApzWheelInput() const override {
       return true;
@@ -325,20 +325,20 @@ private:
     DWRITE_MEASURING_MODE mMeasuringMode;
 
     mozilla::Mutex mDeviceLock;
     RefPtr<IDXGIAdapter1> mAdapter;
     RefPtr<ID3D11Device> mD3D11Device;
     RefPtr<ID3D11Device> mD3D11ContentDevice;
     RefPtr<ID3D11Device> mD3D11ImageBridgeDevice;
     RefPtr<mozilla::layers::DeviceManagerD3D9> mDeviceManager;
-    bool mIsWARP;
+    mozilla::Atomic<bool> mIsWARP;
     bool mHasDeviceReset;
     bool mHasFakeDeviceReset;
-    bool mCompositorD3D11TextureSharingWorks;
+    mozilla::Atomic<bool> mCompositorD3D11TextureSharingWorks;
     mozilla::Atomic<bool> mHasD3D9DeviceReset;
     DeviceResetReason mDeviceResetReason;
 
     RefPtr<mozilla::layers::ReadbackManagerD3D11> mD3D11ReadbackManager;
 
     nsTArray<D3D_FEATURE_LEVEL> mFeatureLevels;
 };