diff --git a/gfx/layers/client/ContentClient.cpp b/gfx/layers/client/ContentClient.cpp
index d65a33b98b0..bf8e4607c0b 100644
--- a/gfx/layers/client/ContentClient.cpp
+++ b/gfx/layers/client/ContentClient.cpp
@@ -148,7 +148,9 @@ ContentClientRemoteBuffer::EndPaint()
   SetBufferProvider(nullptr);
   SetBufferProviderOnWhite(nullptr);
   for (unsigned i = 0; i< mOldTextures.Length(); ++i) {
-    mOldTextures[i]->Unlock();
+    if (mOldTextures[i]->IsLocked()) {
+      mOldTextures[i]->Unlock();
+    }
   }
   mOldTextures.Clear();
 
@@ -557,6 +559,15 @@ ContentClientDoubleBuffered::PrepareFrame()
 {
   mIsNewBuffer = false;
 
+  if (mTextureClient) {
+    DebugOnly<bool> locked = mTextureClient->Lock(OPEN_READ_WRITE);
+    MOZ_ASSERT(locked);
+  }
+  if (mTextureClientOnWhite) {
+    DebugOnly<bool> locked = mTextureClientOnWhite->Lock(OPEN_READ_WRITE);
+    MOZ_ASSERT(locked);
+  }
+
   if (!mFrontAndBackBufferDiffer) {
     return;
   }
diff --git a/gfx/layers/client/TextureClient.h b/gfx/layers/client/TextureClient.h
index 775e2061491..80d05540c73 100644
--- a/gfx/layers/client/TextureClient.h
+++ b/gfx/layers/client/TextureClient.h
@@ -172,6 +172,8 @@ public:
 
   virtual void Unlock() {}
 
+  virtual bool IsLocked() const = 0;
+
   /**
    * Returns true if this texture has a lock/unlock mechanism.
    * Textures that do not implement locking should be immutable or should
@@ -313,6 +315,8 @@ public:
 
   virtual void Unlock() MOZ_OVERRIDE;
 
+  virtual bool IsLocked() const MOZ_OVERRIDE { return mLocked; }
+
   // TextureClientSurface
 
   virtual TextureClientSurface* AsTextureClientSurface() MOZ_OVERRIDE { return this; }
diff --git a/gfx/layers/d3d11/TextureD3D11.h b/gfx/layers/d3d11/TextureD3D11.h
index 0bf6e513655..d510d96c61b 100644
--- a/gfx/layers/d3d11/TextureD3D11.h
+++ b/gfx/layers/d3d11/TextureD3D11.h
@@ -41,6 +41,8 @@ public:
 
   virtual void Unlock() MOZ_OVERRIDE;
 
+  virtual bool IsLocked() const MOZ_OVERRIDE { return mIsLocked; }
+
   virtual bool ToSurfaceDescriptor(SurfaceDescriptor& aOutDescriptor) MOZ_OVERRIDE;
 
   virtual gfx::IntSize GetSize() const MOZ_OVERRIDE { return mSize; }
diff --git a/gfx/layers/d3d9/TextureD3D9.h b/gfx/layers/d3d9/TextureD3D9.h
index b60d487a7fc..a845f53accf 100644
--- a/gfx/layers/d3d9/TextureD3D9.h
+++ b/gfx/layers/d3d9/TextureD3D9.h
@@ -194,6 +194,8 @@ public:
 
   virtual void Unlock() MOZ_OVERRIDE;
 
+  virtual bool IsLocked() const MOZ_OVERRIDE { return mIsLocked; }
+
   virtual bool ToSurfaceDescriptor(SurfaceDescriptor& aOutDescriptor) MOZ_OVERRIDE;
 
   virtual gfx::IntSize GetSize() const { return mSize; }
@@ -242,6 +244,8 @@ public:
 
   virtual void Unlock() MOZ_OVERRIDE;
 
+  virtual bool IsLocked() const MOZ_OVERRIDE { return mIsLocked; }
+
   virtual bool ToSurfaceDescriptor(SurfaceDescriptor& aOutDescriptor) MOZ_OVERRIDE;
 
   virtual gfx::IntSize GetSize() const { return mSize; }
@@ -287,6 +291,8 @@ public:
 
   virtual void Unlock() MOZ_OVERRIDE;
 
+  virtual bool IsLocked() const MOZ_OVERRIDE { return mIsLocked; }
+
   virtual bool ToSurfaceDescriptor(SurfaceDescriptor& aOutDescriptor) MOZ_OVERRIDE;
 
   void InitWith(IDirect3DTexture9* aTexture, HANDLE aSharedHandle, D3DSURFACE_DESC aDesc)
diff --git a/gfx/layers/opengl/TextureClientOGL.cpp b/gfx/layers/opengl/TextureClientOGL.cpp
index 6eb406c7e5e..6ae3ac89c41 100644
--- a/gfx/layers/opengl/TextureClientOGL.cpp
+++ b/gfx/layers/opengl/TextureClientOGL.cpp
@@ -60,6 +60,21 @@ SharedTextureClientOGL::InitWith(gl::SharedTextureHandle aHandle,
   }
 }
 
+bool
+SharedTextureClientOGL::Lock(OpenMode mode)
+{
+  MOZ_ASSERT(!mIsLocked);
+  mIsLocked = true;
+  return true;
+}
+
+void
+SharedTextureClientOGL::Unlock()
+{
+  MOZ_ASSERT(mIsLocked);
+  mIsLocked = false;
+}
+
 bool
 SharedTextureClientOGL::IsAllocated() const
 {
@@ -69,6 +84,7 @@ SharedTextureClientOGL::IsAllocated() const
 StreamTextureClientOGL::StreamTextureClientOGL(TextureFlags aFlags)
   : TextureClient(aFlags)
   , mStream(0)
+  , mIsLocked(false)
 {
 }
 
@@ -77,6 +93,21 @@ StreamTextureClientOGL::~StreamTextureClientOGL()
   // the data is owned externally.
 }
 
+bool
+StreamTextureClientOGL::Lock(OpenMode mode)
+{
+  MOZ_ASSERT(!mIsLocked);
+  mIsLocked = true;
+  return true;
+}
+
+void
+StreamTextureClientOGL::Unlock()
+{
+  MOZ_ASSERT(mIsLocked);
+  mIsLocked = false;
+}
+
 bool
 StreamTextureClientOGL::ToSurfaceDescriptor(SurfaceDescriptor& aOutDescriptor)
 {
diff --git a/gfx/layers/opengl/TextureClientOGL.h b/gfx/layers/opengl/TextureClientOGL.h
index 6afa130711a..e8123767080 100644
--- a/gfx/layers/opengl/TextureClientOGL.h
+++ b/gfx/layers/opengl/TextureClientOGL.h
@@ -40,6 +40,12 @@ public:
 
   virtual bool ToSurfaceDescriptor(SurfaceDescriptor& aOutDescriptor) MOZ_OVERRIDE;
 
+  virtual bool Lock(OpenMode mode) MOZ_OVERRIDE;
+
+  virtual void Unlock() MOZ_OVERRIDE;
+
+  virtual bool IsLocked() const MOZ_OVERRIDE { return mIsLocked; }
+
   void InitWith(gl::SharedTextureHandle aHandle,
                 gfx::IntSize aSize,
                 gl::SharedTextureShareType aShareType,
@@ -61,6 +67,7 @@ protected:
   gfx::IntSize mSize;
   gl::SharedTextureShareType mShareType;
   bool mInverted;
+  bool mIsLocked;
 };
 
 /**
@@ -75,6 +82,12 @@ public:
 
   virtual bool IsAllocated() const MOZ_OVERRIDE;
 
+  virtual bool Lock(OpenMode mode) MOZ_OVERRIDE;
+
+  virtual void Unlock() MOZ_OVERRIDE;
+
+  virtual bool IsLocked() const MOZ_OVERRIDE { return mIsLocked; }
+
   virtual bool ToSurfaceDescriptor(SurfaceDescriptor& aOutDescriptor) MOZ_OVERRIDE;
 
   virtual TextureClientData* DropTextureData() MOZ_OVERRIDE { return nullptr; }
@@ -85,6 +98,7 @@ public:
 
 protected:
   gfx::SurfaceStream* mStream;
+  bool mIsLocked;
 };
 
 class DeprecatedTextureClientSharedOGL : public DeprecatedTextureClient