Revert of Re-enable renderer partial raster by default. (patchset chr…

…omium#1 id:1 of https://codereview.chromium.org/1326103002/ )

Reason for revert:
Exposes caret invalidation bugs (http://crbug.com/528922).

Original issue's description:
> Re-enable renderer partial raster by default.
>
> If you see 1-pixel repainting issues with this CL in the blame list, it is
> likely at fault. This CL should revert cleanly if needed.
>
> BUG=492754
>
> Committed: https://crrev.com/f11aee0769a5a1d37ce4c601dcb2b27dd1338fa7
> Cr-Commit-Position: refs/heads/master@{#347307}

TBR=piman@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=492754,528922

Review URL: https://codereview.chromium.org/1329163002

Cr-Commit-Position: refs/heads/master@{#347765}

content/browser/gpu/compositor_util.cc

@@ -225,7 +225,7 @@ bool IsPersistentGpuMemoryBufferEnabled() {
   if (IsZeroCopyUploadEnabled())
     return false;
   const auto& command_line = *base::CommandLine::ForCurrentProcess();
-  return !command_line.HasSwitch(switches::kDisablePersistentGpuMemoryBuffer);
+  return command_line.HasSwitch(switches::kEnablePersistentGpuMemoryBuffer);
 }
 
 bool IsGpuRasterizationEnabled() {