Add arb_texture_rectangle support properly in GLES3 shaders

src/gpu/gl/builders/GrGLProgramBuilder.cpp

Index: src/gpu/gl/builders/GrGLProgramBuilder.cpp
diff --git a/src/gpu/gl/builders/GrGLProgramBuilder.cpp b/src/gpu/gl/builders/GrGLProgramBuilder.cpp
index 9f4291513c7d6bda0a682646e291e05ef61df566..58520f10e8c60183e25255ce163f9559e910c9e2 100644
--- a/src/gpu/gl/builders/GrGLProgramBuilder.cpp
+++ b/src/gpu/gl/builders/GrGLProgramBuilder.cpp
@@ -97,6 +97,11 @@ void GrGLProgramBuilder::emitSamplers(const GrProcessor& processor,
             SkASSERT(externalFeatureString);
             fFS.addFeature(1 << GrGLSLFragmentShaderBuilder::kExternalTexture_GLSLPrivateFeature,
                            externalFeatureString);
+        } else if (kSampler2DRect_GrSLType == samplerType) {
+            const char* rectangleFeatureString =
+                    this->glslCaps()->rectangleTextureExtensionString();
+            fFS.addFeature(1 << GrGLSLFragmentShaderBuilder::kRectangleTexture_GLSLPrivateFeature,
+                           rectangleFeatureString);
         }
     }
 }