Enable MRT support by exposing glDrawBuffersEXT to the application.

TRAC #22710

Signed-off-by: Geoff Lang
Signed-off-by: Shannon Woods
Author: Jamie Madill

git-svn-id: https://angleproject.googlecode.com/svn/branches/es3proto@2098 736b8ea6-26fd-11df-bfd4-992fa37f6226
diff --git a/src/libGLESv2/Context.cpp b/src/libGLESv2/Context.cpp
index 3e85ce4..f17045a 100644
--- a/src/libGLESv2/Context.cpp
+++ b/src/libGLESv2/Context.cpp
@@ -2583,6 +2583,11 @@
         extensionString += "GL_EXT_texture_format_BGRA8888 ";
     }
 
+    if (mRenderer->getMaxRenderTargets() > 1)
+    {
+        extensionString += "GL_EXT_draw_buffers ";
+    }
+
     extensionString += "GL_EXT_texture_storage ";
 
     // ANGLE-specific extensions