Use base::ScopedTypeRef for CGL types

content/browser/renderer_host/compositing_iosurface_layer_mac.mm

Index: content/browser/renderer_host/compositing_iosurface_layer_mac.mm
diff --git a/content/browser/renderer_host/compositing_iosurface_layer_mac.mm b/content/browser/renderer_host/compositing_iosurface_layer_mac.mm
index b05ffe2d2d74da2410cc94cd78536004ce1cb0a4..2fe7478643634ecde833819087906fe72c8a4e43 100644
--- a/content/browser/renderer_host/compositing_iosurface_layer_mac.mm
+++ b/content/browser/renderer_host/compositing_iosurface_layer_mac.mm
@@ -102,10 +102,26 @@
   // This makes the window content not lag behind the resize (at the cost of
   // blocking on the browser's main thread).
   if (cached_view->render_widget_host_) {
-    cached_view->about_to_validate_and_paint_ = true;
-    (void)cached_view->render_widget_host_->GetBackingStore(true);
-    cached_view->about_to_validate_and_paint_ = false;
-    CGLSetCurrentContext(glContext);
+    // Note that GetBackingStore can potentially spawn a nested run loop, which
+    // may change the current GL context, or, because the GL contexts are
+    // shared, may change the currently-bound FBO. Ensure that, when the run
+    // loop returns, the original GL context remain current, and the original
+    // FBO remain bound.
+    // TODO(ccameron): This is far too fragile a mechanism to rely on. Find
+    // a way to avoid doing this.

[ccameron, 2014/02/07 01:11:30]

Note that this isn't anything new with this patch  -- just documentation and
robust-ifying the existing scheme. This scheme is part of the way CAOpenGLLayer
does drawing (which is also how non-CA paths do this). I'd like to change this
to a way that we don't pause in the drawing code, but rather delay the actual
resizes.

+    GLuint previous_framebuffer = 0;
+    glGetIntegerv(GL_FRAMEBUFFER_BINDING,
+                  reinterpret_cast<GLint*>(&previous_framebuffer));
+    CHECK(glCheckFramebufferStatus(GL_FRAMEBUFFER) == GL_FRAMEBUFFER_COMPLETE);
+    {
+      gfx::ScopedCGLSetCurrentContext scoped_set_current_context(NULL);
+      cached_view->about_to_validate_and_paint_ = true;
+      (void)cached_view->render_widget_host_->GetBackingStore(true);
+      cached_view->about_to_validate_and_paint_ = false;
+    }
+    DCHECK_EQ(CGLGetCurrentContext(), glContext)
+        << "original GL context failed to re-bind, browser crash is imminent.";
+    glBindFramebuffer(GL_FRAMEBUFFER, previous_framebuffer);
   }
 
   // If a transition to software mode has occurred, this layer should be