Bug 1617751 - Ensure that GLScreenBuffer back buffer is created using the newly attached factory. r=jgilbert

Differential Revision: https://phabricator.services.mozilla.com/D64183

--HG--
extra : moz-landing-system : lando

dom/canvas/WebGLContext.cpp

@@ -952,6 +952,12 @@ Maybe<ICRData> WebGLContext::InitializeCanvasRenderer(
 
   gl->Screen()->Morph(std::move(factory));
 
+#if defined(MOZ_WIDGET_ANDROID)
+  // On Android we are using a different GLScreenBuffer for WebVR, so we need
+  // a resize here because PresentScreenBuffer() may not be called for the
+  // gl->Screen() after we set the new factory.
+  mForceResizeOnPresent = true;
+#endif
   mVRReady = true;
   return Some(ret);
 }
@@ -978,12 +984,14 @@ bool WebGLContext::PresentScreenBuffer(gl::GLScreenBuffer* const targetScreen) {
   if (!ValidateAndInitFB(nullptr)) return false;
 
   const auto& screen = targetScreen ? targetScreen : gl->Screen();
-  if ((!screen->IsReadBufferReady() || screen->Size() != mDefaultFB->mSize) &&
+  if ((!screen->IsReadBufferReady() || mForceResizeOnPresent ||
+       screen->Size() != mDefaultFB->mSize) &&
       !screen->Resize(mDefaultFB->mSize)) {
     GenerateWarning("screen->Resize failed. Losing context.");
     LoseContext();
     return false;
   }
+  mForceResizeOnPresent = false;
 
   gl->fBindFramebuffer(LOCAL_GL_FRAMEBUFFER, 0);
   BlitBackbufferToCurDriverFB();

dom/canvas/WebGLContext.h

@@ -849,6 +849,7 @@ class WebGLContext : public VRefCounted, public SupportsWeakPtr<WebGLContext> {
   bool mCanLoseContextInForeground = true;
   bool mShouldPresent = false;
   bool mDisableFragHighP = false;
+  bool mForceResizeOnPresent = false;
   bool mVRReady = false;
 
   template <typename WebGLObjectType>