Initial version of external_oes texture support and unit test

src/gpu/glsl/GrGLSL.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrGLSL_DEFINED
 #define GrGLSL_DEFINED
 
@@ skipping 67 matching lines @@
         case kVec3f_GrSLType:
             return "vec3";
         case kVec4f_GrSLType:
             return "vec4";
         case kMat33f_GrSLType:
             return "mat3";
         case kMat44f_GrSLType:
             return "mat4";
         case kSampler2D_GrSLType:
             return "sampler2D";
+        case kSamplerExternal_GrSLType:
+            return "samplerExternalOES";
         default:
             SkFAIL("Unknown shader var type.");
             return ""; // suppress warning
     }
 }
 
 /** A generic base-class representing a GLSL expression.
  * The instance can be a variable name, expression or vecN(0) or vecN(1). Does simple constant
  * folding with help of 1 and 0.
  *
@@ skipping 228 matching lines @@
 
 /**
  * Does an inplace mul, *=, of vec4VarName by mulFactor.
  * A semicolon is added after the assignment.
  */
 void GrGLSLMulVarBy4f(SkString* outAppend, const char* vec4VarName, const GrGLSLExpr4& mulFactor);
 
 #include "GrGLSL_impl.h"
 
 #endif