Revert of Don't expose --disable-gpu-compositing, only set internally....

Revert of Don't expose --disable-gpu-compositing, only set internally. (https://codereview.chromium.org/300523002/)

Reason for revert:
Makes a bunch of virtual/softwarecompositing tests Timeout on Mac
https://code.google.com/p/chromium/issues/detail?id=377145

Original issue's description:
> Don't expose --disable-gpu-compositing, only set internally.
> 
> The flag isn't meant to be set externally, it doesn't work on most
> configs. It's only meant internally to make sure the renderer doesn't
> try to use GPU when the browser is in software.
> 
> BUG=None
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=272636

TBR=jbauman@chromium.org,piman@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=None

Review URL: https://codereview.chromium.org/299383002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@272707 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/chromeos/login/chrome_restart_request.cc

@@ -79,6 +79,7 @@ std::string DeriveCommandLine(const GURL& start_url,
     ::switches::kDisableFiltersOverIPC,
     ::switches::kDisableGpuShaderDiskCache,
     ::switches::kDisableGpuWatchdog,
+    ::switches::kDisableGpuCompositing,
     ::switches::kDisableGpuRasterization,
     ::switches::kDisableImplSidePainting,
     ::switches::kDisableLowResTiling,

content/browser/renderer_host/render_process_host_impl.cc

@@ -1038,6 +1038,7 @@ void RenderProcessHostImpl::PropagateBrowserCommandLineToRenderer(
     switches::kDisableFastTextAutosizing,
     switches::kDisableFileSystem,
     switches::kDisableFiltersOverIPC,
+    switches::kDisableGpuCompositing,
     switches::kDisableGpuVsync,
     switches::kDisableLowResTiling,
     switches::kDisableHistogramCustomizer,

content/public/common/content_switches.h

@@ -59,7 +59,7 @@ CONTENT_EXPORT extern const char kDisableFlashStage3d[];
 CONTENT_EXPORT extern const char kDisableGestureTapHighlight[];
 CONTENT_EXPORT extern const char kDisableGLMultisampling[];
 CONTENT_EXPORT extern const char kDisableGpu[];
-extern const char kDisableGpuCompositing[];
+CONTENT_EXPORT extern const char kDisableGpuCompositing[];
 extern const char kDisableGpuProcessCrashLimit[];
 CONTENT_EXPORT extern const char kDisableGpuRasterization[];
 CONTENT_EXPORT extern const char kDisableGpuSandbox[];