Add a flag to allow renderer to use software compositor when GL compositor doesn't work.

content/public/common/content_switches.h

Index: content/public/common/content_switches.h
diff --git a/content/public/common/content_switches.h b/content/public/common/content_switches.h
index 434577ee76281f6b326fd23c7bb698f862dbb4ac..bbe0d6b5a6b58c0d8220c00ddff01781019896fc 100644
--- a/content/public/common/content_switches.h
+++ b/content/public/common/content_switches.h
@@ -56,6 +56,7 @@ CONTENT_EXPORT extern const char kDisableGLMultisampling[];
 CONTENT_EXPORT extern const char kDisableGpuProcessPrelaunch[];
 extern const char kDisableGpuSandbox[];
 extern const char kReduceGpuSandbox[];
+CONTENT_EXPORT extern const char kDisableGpuCompositing[];
 extern const char kDisableGpuWatchdog[];
 CONTENT_EXPORT extern const char kDisableHangMonitor[];
 CONTENT_EXPORT extern const char kDisableHTMLNotifications[];
@@ -146,7 +147,7 @@ extern const char kEnablePruneGpuCommandBuffers[];
 extern const char kEnableSSLCachedInfo[];
 extern const char kEnableSandboxLogging[];
 extern const char kEnableSpatialNavigation[];
-CONTENT_EXPORT extern const char kEnableSoftwareCompositingGLAdapter[];
+CONTENT_EXPORT extern const char kEnableSoftwareCompositing[];
 CONTENT_EXPORT extern const char kEnableSmoothScrolling[];
 CONTENT_EXPORT extern const char kEnableStatsTable[];
 extern const char kEnableStrictSiteIsolation[];