Add future sync point methods to ContextSupport.

gpu/GLES2/extensions/CHROMIUM/CHROMIUM_sync_point.txt

Index: gpu/GLES2/extensions/CHROMIUM/CHROMIUM_sync_point.txt
diff --git a/gpu/GLES2/extensions/CHROMIUM/CHROMIUM_sync_point.txt b/gpu/GLES2/extensions/CHROMIUM/CHROMIUM_sync_point.txt
index bc8665a306494e70d28f3cbe6d38746cb684aeb2..bae22e47caa45ddb84cc691babcb2f2c787ea001 100644
--- a/gpu/GLES2/extensions/CHROMIUM/CHROMIUM_sync_point.txt
+++ b/gpu/GLES2/extensions/CHROMIUM/CHROMIUM_sync_point.txt
@@ -8,7 +8,7 @@ Name Strings
 
 Version
 
-    Last Modifed Date: February 25, 2013
+    Last Modifed Date: July 1, 2014
 
 Dependencies
 
@@ -48,6 +48,26 @@ New Procedures and Functions
     namespace is shared between all contexts on the same server, including other
     context groups.
 
+    The command
+
+        uint InsertFutureSyncPointCHROMIUM()
+
+    creates a sync point, but does not insert it into the stream of commands.
+    The returned sync point name can be waited on immediately, but will not be
+    signalled until a retire command is sent, or until the context is
+    destroyed, whichever happens first. This command may only be permitted if
+    a context is "trusted", which is defined by the implementation.

[piman, 2014/07/11 22:24:32]

nit: could we add a static query, or an extension string (e.g.
CHROMIUM_sync_point_trusted) so that the client can test it?

+
+    The command
+
+        void RetireSyncPointCHROMIUM(uint sync_point)
+
+    causes a sync point to be signaled as soon as the previous commands have
+    been submitted to the server. The sync point named <sync_point> must have
+    been returned by InsertFutureSyncPointCHROMIUM. The sync point name will
+    be implicitly deleted when it becomes signaled. This command may only be
+    permitted if a context is "trusted", which is defined by the
+    implementation.
 
     The command
 
@@ -70,4 +90,5 @@ New State
 
 Revision History
 
+    7/1/2014     Added future sync points.
     2/25/2013    Documented the extension