Added knowledge of GL_RED textures to debugGLReadPixels

http://codereview.appspot.com/6257070/



git-svn-id: http://skia.googlecode.com/svn/trunk@4071 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/gl/debug/GrGLCreateDebugInterface.cpp b/src/gpu/gl/debug/GrGLCreateDebugInterface.cpp
index 685e18d..5419bff 100644
--- a/src/gpu/gl/debug/GrGLCreateDebugInterface.cpp
+++ b/src/gpu/gl/debug/GrGLCreateDebugInterface.cpp
@@ -163,6 +163,9 @@
         case GR_GL_RGB:
             componentsPerPixel = 3;
             break;
+        case GR_GL_RED:
+            componentsPerPixel = 1;
+            break;
         default:
             GrAlwaysAssert(false);
             break;