Fix decl of gl_FragCoord in GLSL versions <= 1.20.

We we're saying "in" instead of "varying".
Review URL: https://codereview.appspot.com/6779043

git-svn-id: http://skia.googlecode.com/svn/trunk@6104 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/gl/GrGLShaderBuilder.cpp b/src/gpu/gl/GrGLShaderBuilder.cpp
index 394b42f..a915cfa 100644
--- a/src/gpu/gl/GrGLShaderBuilder.cpp
+++ b/src/gpu/gl/GrGLShaderBuilder.cpp
@@ -289,7 +289,11 @@
     if (fContext.caps().fragCoordConventionsSupport()) {
         if (!fSetupFragPosition) {
             fFSHeader.append("#extension GL_ARB_fragment_coord_conventions: require\n");
-            fFSHeader.append("layout(origin_upper_left) in vec4 gl_FragCoord;\n");
+            fFSInputs.push_back().set(kVec4f_GrSLType,
+                                      GrGLShaderVar::kIn_TypeModifier,
+                                      "gl_FragCoord",
+                                      GrGLShaderVar::kDefault_Precision,
+                                      GrGLShaderVar::kUpperLeft_Origin);
             fSetupFragPosition = true;
         }
         return "gl_FragCoord";