Make --disable-gpu-compositing disable browser compositor as well.

content/browser/gpu/compositor_util.cc

Index: content/browser/gpu/compositor_util.cc
diff --git a/content/browser/gpu/compositor_util.cc b/content/browser/gpu/compositor_util.cc
index 3669a06170dda66dafd87081addb73ac29d61a07..ba27c1224d457d44c7fc1a67e7f5bccedf88daad 100644
--- a/content/browser/gpu/compositor_util.cc
+++ b/content/browser/gpu/compositor_util.cc
@@ -61,7 +61,7 @@ const GpuFeatureInfo GetGpuFeatureInfo(size_t index, bool* eof) {
       {
           kGpuCompositingFeatureName,
           manager->IsFeatureBlacklisted(gpu::GPU_FEATURE_TYPE_GPU_COMPOSITING),
-          false,
+          command_line.HasSwitch(switches::kDisableGpuCompositing),
           "Gpu compositing has been disabled, either via about:flags or"
           " command line. The browser will fall back to software compositing"
           " and hardware acceleration will be unavailable.",