Initial version of external_oes texture support and unit test

src/gpu/gl/GrGLProgramDataManager.cpp

Index: src/gpu/gl/GrGLProgramDataManager.cpp
diff --git a/src/gpu/gl/GrGLProgramDataManager.cpp b/src/gpu/gl/GrGLProgramDataManager.cpp
index 7320b2dd8a44fa0b7b84310a7d5b027b7f69e7e3..c6a0e73172e122cb3570570ab2503cde6b5d8dd8 100644
--- a/src/gpu/gl/GrGLProgramDataManager.cpp
+++ b/src/gpu/gl/GrGLProgramDataManager.cpp
@@ -62,7 +62,7 @@ GrGLProgramDataManager::GrGLProgramDataManager(GrGLGpu* gpu, GrGLuint programID,
 
 void GrGLProgramDataManager::setSampler(UniformHandle u, int texUnit) const {
     const Uniform& uni = fUniforms[u.toIndex()];
-    SkASSERT(uni.fType == kSampler2D_GrSLType);
+    SkASSERT(uni.fType == kSampler2D_GrSLType || uni.fType == kSamplerExternal_GrSLType);
     SkASSERT(GrGLSLShaderVar::kNonArray == uni.fArrayCount);
     // FIXME: We still insert a single sampler uniform for every stage. If the shader does not
     // reference the sampler then the compiler may have optimized it out. Uncomment this assert