DrawingBuffer: Add checks for state restorer

We're crashing due to a null m_stateRestorer in the fuzzer. It's unclear
how this is possible, so add CHECKs to indicate where this is going
wrong.

These CHECKS should be changed to DCHECKs when the issue is addressed.

BUG=658265

Review-Url: https://codereview.chromium.org/2439073003
Cr-Commit-Position: refs/heads/master@{#427197}

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

@@ -251,6 +251,8 @@ bool DrawingBuffer::prepareTextureMailboxInternal(
     cc::TextureMailbox* outMailbox,
     std::unique_ptr<cc::SingleReleaseCallback>* outReleaseCallback,
     bool forceGpuResult) {
+  // TODO(ccameron): Make this a DCHECK after fixing crbug.com/658265
+  CHECK(m_stateRestorer);
   if (m_destructionInProgress) {
     // It can be hit in the following sequence.
     // 1. WebGL draws something.
@@ -320,6 +322,8 @@ bool DrawingBuffer::finishPrepareTextureMailboxSoftware(
 bool DrawingBuffer::finishPrepareTextureMailboxGpu(
     cc::TextureMailbox* outMailbox,
     std::unique_ptr<cc::SingleReleaseCallback>* outReleaseCallback) {
+  // TODO(ccameron): Make this a DCHECK after fixing crbug.com/658265
+  CHECK(m_stateRestorer);
   if (m_webGLVersion > WebGL1) {
     m_stateRestorer->setPixelUnpackBufferBindingDirty();
     m_gl->BindBuffer(GL_PIXEL_UNPACK_BUFFER, 0);
@@ -567,6 +571,8 @@ DrawingBuffer::textureColorBufferParameters() {
 
 PassRefPtr<DrawingBuffer::ColorBuffer>
 DrawingBuffer::createOrRecycleColorBuffer() {
+  // TODO(ccameron): Make this a DCHECK after fixing crbug.com/658265
+  CHECK(m_stateRestorer);
   if (!m_recycledColorBufferQueue.isEmpty()) {
     RefPtr<ColorBuffer> recycled = m_recycledColorBufferQueue.takeLast();
     if (recycled->receiveSyncToken.HasData())
@@ -802,6 +808,8 @@ void DrawingBuffer::beginDestruction() {
 }
 
 bool DrawingBuffer::resizeDefaultFramebuffer(const IntSize& size) {
+  // TODO(ccameron): Make this a DCHECK after fixing crbug.com/658265
+  CHECK(m_stateRestorer);
   // Recreate m_backColorBuffer.
   m_backColorBuffer = createColorBuffer(size);
 
@@ -870,6 +878,8 @@ void DrawingBuffer::clearFramebuffers(GLbitfield clearMask) {
 }
 
 void DrawingBuffer::clearFramebuffersInternal(GLbitfield clearMask) {
+  // TODO(ccameron): Make this a DCHECK after fixing crbug.com/658265
+  CHECK(m_stateRestorer);
   m_stateRestorer->setFramebufferBindingDirty();
   // We will clear the multisample FBO, but we also need to clear the
   // non-multisampled buffer.
@@ -905,6 +915,8 @@ bool DrawingBuffer::resize(const IntSize& newSize) {
 }
 
 bool DrawingBuffer::resizeFramebufferInternal(const IntSize& newSize) {
+  // TODO(ccameron): Make this a DCHECK after fixing crbug.com/658265
+  CHECK(m_stateRestorer);
   CHECK(!newSize.isEmpty());
   IntSize adjustedSize = adjustSize(newSize, m_size, m_maxTextureSize);
   if (adjustedSize.isEmpty())
@@ -960,6 +972,8 @@ void DrawingBuffer::resolveAndBindForReadAndDraw() {
 }
 
 void DrawingBuffer::resolveMultisampleFramebufferInternal() {
+  // TODO(ccameron): Make this a DCHECK after fixing crbug.com/658265
+  CHECK(m_stateRestorer);
   m_stateRestorer->setFramebufferBindingDirty();
   if (wantExplicitResolve() && !m_contentsChangeCommitted) {
     m_stateRestorer->setClearStateDirty();
@@ -1068,6 +1082,8 @@ void DrawingBuffer::readBackFramebuffer(unsigned char* pixels,
                                         int height,
                                         ReadbackOrder readbackOrder,
                                         WebGLImageConversion::AlphaOp op) {
+  // TODO(ccameron): Make this a DCHECK after fixing crbug.com/658265
+  CHECK(m_stateRestorer);
   m_stateRestorer->setPixelPackAlignmentDirty();
   m_gl->PixelStorei(GL_PACK_ALIGNMENT, 1);
   m_gl->ReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, pixels);
@@ -1112,6 +1128,8 @@ void DrawingBuffer::flipVertically(uint8_t* framebuffer,
 
 RefPtr<DrawingBuffer::ColorBuffer> DrawingBuffer::createColorBuffer(
     const IntSize& size) {
+  // TODO(ccameron): Make this a DCHECK after fixing crbug.com/658265
+  CHECK(m_stateRestorer);
   m_stateRestorer->setFramebufferBindingDirty();
   m_stateRestorer->setTextureBindingDirty();
 
@@ -1185,6 +1203,8 @@ RefPtr<DrawingBuffer::ColorBuffer> DrawingBuffer::createColorBuffer(
 }
 
 void DrawingBuffer::attachColorBufferToReadFramebuffer() {
+  // TODO(ccameron): Make this a DCHECK after fixing crbug.com/658265
+  CHECK(m_stateRestorer);
   m_stateRestorer->setFramebufferBindingDirty();
   m_stateRestorer->setTextureBindingDirty();
 
@@ -1228,11 +1248,14 @@ GLenum DrawingBuffer::getMultisampledRenderbufferFormat() {
 DrawingBuffer::ScopedStateRestorer::ScopedStateRestorer(
     DrawingBuffer* drawingBuffer)
     : m_drawingBuffer(drawingBuffer) {
-  DCHECK(!m_drawingBuffer->m_stateRestorer);
+  // TODO(ccameron): Make this a DCHECK after fixing crbug.com/658265
+  CHECK(!m_drawingBuffer->m_stateRestorer);
   m_drawingBuffer->m_stateRestorer = this;
 }
 
 DrawingBuffer::ScopedStateRestorer::~ScopedStateRestorer() {
+  // TODO(ccameron): Make this a DCHECK after fixing crbug.com/658265
+  CHECK_EQ(m_drawingBuffer->m_stateRestorer, this);
   m_drawingBuffer->m_stateRestorer = nullptr;
   Client* client = m_drawingBuffer->m_client;
   if (!client)