Bug 1337281 - Fix WebRenderAPI::Readback() r=nical

gfx/webrender_bindings/WebRenderAPI.cpp

@@ -196,7 +196,7 @@ WebRenderAPI::Readback(gfx::IntSize size,
             virtual void Run(RenderThread& aRenderThread, WindowId aWindowId) override
             {
                 aRenderThread.UpdateAndRender(aWindowId);
-                wr_readback_into_buffer(mSize.width, mSize.height, mBuffer, mBufferSize);
+                wr_renderer_readback(mSize.width, mSize.height, mBuffer, mBufferSize);
                 layers::AutoCompleteTask complete(mTask);
             }
 

gfx/webrender_bindings/webrender_ffi.h

@@ -501,6 +501,13 @@ wr_readback_into_buffer(uint32_t width, uint32_t height,
                         uint8_t* dst_buffer, size_t buffer_length)
 WR_FUNC;
 
+// It is the responsibility of the caller to manage the dst_buffer memory
+// and also free it at the proper time.
+WR_INLINE const uint8_t*
+wr_renderer_readback(uint32_t width, uint32_t height,
+                     uint8_t* dst_buffer, size_t buffer_length)
+WR_FUNC;
+
 // TODO: Remove.
 WR_INLINE void
 wr_profiler_set_enabled(WrWindowState* wrWindow, bool enabled)