Revert "Add a glFlush to GLContextCGL's Make/ReleaseVirtuallyCurrent"

This reverts https://crrev.com/580656 because it re-introduced driver
crashes on macOS.

This don't re-introduce the logging that had been added (yet) because
this patch is to target merging for M69.

TBR=kbr

Bug: 863817
Change-Id: I5912f25416d11606fa335d3955a70478a5edf6fb
Reviewed-on: https://chromium-review.googlesource.com/1163180
Reviewed-by: ccameron <ccameron@chromium.org>
Commit-Queue: ccameron <ccameron@chromium.org>
Cr-Commit-Position: refs/heads/master@{#580787}

gpu/command_buffer/service/gl_context_virtual.cc

@@ -110,6 +110,10 @@ uint64_t GLContextVirtual::BackpressureFenceCreate() {
 void GLContextVirtual::BackpressureFenceWait(uint64_t fence) {
   shared_context_->BackpressureFenceWait(fence);
 }
+
+void GLContextVirtual::FlushForDriverCrashWorkaround() {
+  shared_context_->FlushForDriverCrashWorkaround();
+}
 #endif
 
 GLContextVirtual::~GLContextVirtual() {

gpu/command_buffer/service/gl_context_virtual.h

@@ -50,6 +50,7 @@ class GPU_GLES2_EXPORT GLContextVirtual : public gl::GLContext {
 #if defined(OS_MACOSX)
   uint64_t BackpressureFenceCreate() override;
   void BackpressureFenceWait(uint64_t fence) override;
+  void FlushForDriverCrashWorkaround() override;
 #endif
 
  protected:

gpu/command_buffer/service/gles2_cmd_decoder.cc

@@ -5690,6 +5690,13 @@ error::Error GLES2DecoderImpl::DoCommandsImpl(unsigned int num_commands,
     }
   }
 
+#if defined(OS_MACOSX)
+  // Aggressively call glFlush on macOS. This is the only fix that has been
+  // found so far to avoid crashes on Intel drivers.
+  // https://crbug.com/863817
+  context_->FlushForDriverCrashWorkaround();
+#endif
+
   *entries_processed = process_pos;
 
   if (error::IsError(result)) {

ui/gl/gl_context.cc

@@ -194,6 +194,8 @@ uint64_t GLContext::BackpressureFenceCreate() {
 }
 
 void GLContext::BackpressureFenceWait(uint64_t fence) {}
+
+void GLContext::FlushForDriverCrashWorkaround() {}
 #endif
 
 bool GLContext::HasExtension(const char* name) {

ui/gl/gl_context.h

@@ -162,12 +162,11 @@ class GL_EXPORT GLContext : public base::RefCounted<GLContext> {
   virtual bool WasAllocatedUsingRobustnessExtension();
 
   // Make this context current when used for context virtualization.
-  virtual bool MakeVirtuallyCurrent(GLContext* virtual_context,
-                                    GLSurface* surface);
+  bool MakeVirtuallyCurrent(GLContext* virtual_context, GLSurface* surface);
 
   // Notify this context that |virtual_context|, that was using us, is
   // being released or destroyed.
-  virtual void OnReleaseVirtuallyCurrent(GLContext* virtual_context);
+  void OnReleaseVirtuallyCurrent(GLContext* virtual_context);
 
   // Returns the GL version string. The context must be current.
   virtual std::string GetGLVersion();
@@ -203,6 +202,9 @@ class GL_EXPORT GLContext : public base::RefCounted<GLContext> {
   virtual uint64_t BackpressureFenceCreate();
   // Perform a client-side wait on a previously-created fence.
   virtual void BackpressureFenceWait(uint64_t fence);
+  // Flush the underlying context to avoid crashes due to driver bugs on macOS.
+  // https://crbug.com/863817
+  virtual void FlushForDriverCrashWorkaround();
 #endif
 
  protected:

ui/gl/gl_context_cgl.cc

@@ -214,33 +214,6 @@ bool GLContextCGL::ForceGpuSwitchIfNeeded() {
   return true;
 }
 
-void GLContextCGL::OnReleaseVirtuallyCurrent(GLContext* virtual_context) {
-  TRACE_EVENT0("gpu", "GLContextCGL::OnReleaseVirtuallyCurrent");
-  // Flush before switching contexts, to avoid driver crashes.
-  // https://crbug.com/863817
-  if (IsCurrent(nullptr))
-    glFlush();
-  GLContext::OnReleaseVirtuallyCurrent(virtual_context);
-}
-
-bool GLContextCGL::MakeVirtuallyCurrent(GLContext* virtual_context,
-                                        GLSurface* surface) {
-  TRACE_EVENT0("gpu", "GLContextCGL::MakeVirtuallyCurrent");
-  // Flush before restoring the new context's state, to avoid driver crashes.
-  // https://crbug.com/863817
-  if (IsCurrent(nullptr))
-    glFlush();
-
-  // Restore the state of the new context.
-  if (!GLContext::MakeVirtuallyCurrent(virtual_context, surface))
-    return false;
-
-  // Flush after having restored this context's state, to avoid driver crashes.
-  // https://crbug.com/863817
-  glFlush();
-  return true;
-}
-
 YUVToRGBConverter* GLContextCGL::GetYUVToRGBConverter(
     const gfx::ColorSpace& color_space) {
   std::unique_ptr<YUVToRGBConverter>& yuv_to_rgb_converter =
@@ -256,6 +229,10 @@ constexpr uint64_t kInvalidFenceId = 0;
 uint64_t GLContextCGL::BackpressureFenceCreate() {
   TRACE_EVENT0("gpu", "GLContextCGL::BackpressureFenceCreate");
 
+  // This flush will trigger a crash if FlushForDriverCrashWorkaround is not
+  // called sufficiently frequently.
+  glFlush();
+
   if (gl::GLFence::IsSupported()) {
     next_backpressure_fence_ += 1;
     backpressure_fences_[next_backpressure_fence_] = GLFence::Create();
@@ -310,6 +287,12 @@ void GLContextCGL::BackpressureFenceWait(uint64_t fence_id) {
     backpressure_fences_.erase(backpressure_fences_.begin());
 }
 
+void GLContextCGL::FlushForDriverCrashWorkaround() {
+  if (!context_ || CGLGetCurrentContext() != context_)
+    return;
+  glFlush();
+}
+
 bool GLContextCGL::MakeCurrent(GLSurface* surface) {
   DCHECK(context_);
 

ui/gl/gl_context_cgl.h

@@ -34,13 +34,11 @@ class GL_EXPORT GLContextCGL : public GLContextReal {
   void* GetHandle() override;
   void SetSafeToForceGpuSwitch() override;
   bool ForceGpuSwitchIfNeeded() override;
-  void OnReleaseVirtuallyCurrent(GLContext* virtual_context) override;
-  bool MakeVirtuallyCurrent(GLContext* virtual_context,
-                            GLSurface* surface) override;
   YUVToRGBConverter* GetYUVToRGBConverter(
       const gfx::ColorSpace& color_space) override;
   uint64_t BackpressureFenceCreate() override;
   void BackpressureFenceWait(uint64_t fence) override;
+  void FlushForDriverCrashWorkaround() override;
 
  protected:
   ~GLContextCGL() override;