Fix non-anti-aliased frame update.

third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp

 /*
  * Copyright (c) 2010, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 150 matching lines @@
                        TRACE_EVENT_SCOPE_GLOBAL);
 }
 
 DrawingBuffer::~DrawingBuffer() {
   DCHECK(m_destructionInProgress);
   m_layer.reset();
   m_contextProvider.reset();
 }
 
 bool DrawingBuffer::markContentsChanged() {
-  if (m_contentsChangeCommitted || !m_contentsChanged) {
-    m_contentsChangeCommitted = false;
+  if (m_contentsChangeResolved || !m_contentsChanged) {
+    m_contentsChangeResolved = false;
     m_contentsChanged = true;
     return true;
   }
   return false;
 }
 
 bool DrawingBuffer::bufferClearNeeded() const {
   return m_bufferClearNeeded;
 }
 
@@ skipping 94 matching lines @@
   // be trying to get a new context and may change modes.
   if (m_gl->GetGraphicsResetStatusKHR() != GL_NO_ERROR)
     return false;
 
   TRACE_EVENT0("blink,rail", "DrawingBuffer::prepareMailbox");
 
   if (m_newMailboxCallback)
     (*m_newMailboxCallback)();
 
   // Resolve the multisampled buffer into m_backColorBuffer texture.
-  if (m_antiAliasingMode != None)
-    resolveMultisampleFramebufferInternal();
+  resolve();
 
   if (m_softwareRendering && !forceGpuResult) {
     return finishPrepareTextureMailboxSoftware(outMailbox, outReleaseCallback);
   } else {
     return finishPrepareTextureMailboxGpu(outMailbox, outReleaseCallback);
   }
 }
 
 bool DrawingBuffer::finishPrepareTextureMailboxSoftware(
     cc::TextureMailbox* outMailbox,
@@ skipping 389 matching lines @@
                                           GLenum destType,
                                           GLint level,
                                           bool premultiplyAlpha,
                                           bool flipY,
                                           const IntPoint& destTextureOffset,
                                           const IntRect& sourceSubRectangle,
                                           SourceDrawingBuffer sourceBuffer) {
   ScopedStateRestorer scopedStateRestorer(this);
 
   if (m_contentsChanged) {
-    if (m_antiAliasingMode != None)
-      resolveMultisampleFramebufferInternal();
+    resolve();
     m_gl->Flush();
   }
 
   // Assume that the destination target is GL_TEXTURE_2D.
   if (!Extensions3DUtil::canUseCopyTextureCHROMIUM(
           GL_TEXTURE_2D, internalFormat, destType, level))
     return false;
 
   // Contexts may be in a different share group. We must transfer the texture
   // through a mailbox first.
@@ skipping 254 matching lines @@
     m_gl->StencilMaskSeparate(GL_FRONT, 0xFFFFFFFF);
   }
 
   clearFramebuffersInternal(clearMask);
   return true;
 }
 
 void DrawingBuffer::resolveAndBindForReadAndDraw() {
   {
     ScopedStateRestorer scopedStateRestorer(this);
-    resolveMultisampleFramebufferInternal();
+    resolve();
   }
   m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_fbo);
 }
 
 void DrawingBuffer::resolveMultisampleFramebufferInternal() {
   DCHECK(m_stateRestorer);
   m_stateRestorer->setFramebufferBindingDirty();
-  if (wantExplicitResolve() && !m_contentsChangeCommitted) {
+  if (wantExplicitResolve() && !m_contentsChangeResolved) {
     m_stateRestorer->setClearStateDirty();
     m_gl->BindFramebuffer(GL_READ_FRAMEBUFFER_ANGLE, m_multisampleFBO);
     m_gl->BindFramebuffer(GL_DRAW_FRAMEBUFFER_ANGLE, m_fbo);
     m_gl->Disable(GL_SCISSOR_TEST);
 
     int width = m_size.width();
     int height = m_size.height();
     // Use NEAREST, because there is no scale performed during the blit.
     GLuint filter = GL_NEAREST;
 
     m_gl->BlitFramebufferCHROMIUM(0, 0, width, height, 0, 0, width, height,
                                   GL_COLOR_BUFFER_BIT, filter);
 
     // On old AMD GPUs on OS X, glColorMask doesn't work correctly for
     // multisampled renderbuffers and the alpha channel can be overwritten.
     // Clear the alpha channel of |m_fbo|.
     if (defaultBufferRequiresAlphaChannelToBePreserved() &&
         contextProvider()
             ->getCapabilities()
             .disable_multisampling_color_mask_usage) {
       m_gl->ClearColor(0, 0, 0, 1);
       m_gl->ColorMask(false, false, false, true);
       m_gl->Clear(GL_COLOR_BUFFER_BIT);
     }
   }
 
   m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_fbo);
   if (m_antiAliasingMode == ScreenSpaceAntialiasing)
     m_gl->ApplyScreenSpaceAntialiasingCHROMIUM();
-  m_contentsChangeCommitted = true;
+}
+
+void DrawingBuffer::resolve() {

[Justin Novosad, 2017/03/31 20:26:53]

Nit: In blink, we like to use the suffix "IfNeeded" for methods that only do
something under certain conditions.

+  if (m_antiAliasingMode != None)
+    resolveMultisampleFramebufferInternal();
+  m_contentsChangeResolved = true;
 }
 
 void DrawingBuffer::restoreFramebufferBindings() {
   m_client->DrawingBufferClientRestoreFramebufferBinding();
 }
 
 void DrawingBuffer::restoreAllState() {
   m_client->DrawingBufferClientRestoreScissorTest();
   m_client->DrawingBufferClientRestoreMaskAndClearValues();
   m_client->DrawingBufferClientRestorePixelPackAlignment();
@@ skipping 269 matching lines @@
   if (m_pixelUnpackBufferBindingDirty)
     client->DrawingBufferClientRestorePixelUnpackBufferBinding();
 }
 
 bool DrawingBuffer::shouldUseChromiumImage() {
   return RuntimeEnabledFeatures::webGLImageChromiumEnabled() &&
          m_chromiumImageUsage == AllowChromiumImage;
 }
 
 }  // namespace blink