Implement support for using GL ES 3.0 with command buffer

tools/flags/SkCommonFlagsConfig.cpp

Index: tools/flags/SkCommonFlagsConfig.cpp
diff --git a/tools/flags/SkCommonFlagsConfig.cpp b/tools/flags/SkCommonFlagsConfig.cpp
index e2aa3270f2dd15ab681476f05cb3e71c45d7bd1b..c3f2932cc98aec755b02026e47c8aef071fbbaed 100644
--- a/tools/flags/SkCommonFlagsConfig.cpp
+++ b/tools/flags/SkCommonFlagsConfig.cpp
@@ -64,6 +64,7 @@ static const char configExtendedHelp[] =
 #endif
 #if SK_COMMAND_BUFFER
     "\t\tcommandbuffer\t\tUse command buffer.\n"
+    "\t\tcommandbuffer3\t\tUse command buffer ES 3.0 (experimental).\n"
 #endif
 #if SK_MESA
     "\t\tmesa\t\t\tUse MESA.\n"
@@ -217,6 +218,10 @@ static bool parse_option_gpu_api(const SkString& value,
         *outContextType = GrContextFactory::kCommandBuffer_GLContextType;
         return true;
     }
+    if (value.equals("commandbuffer3")) {
+        *outContextType = GrContextFactory::kCommandBufferES3_GLContextType;
+        return true;
+    }
 #endif
 #if SK_MESA
     if (value.equals("mesa")) {