Add "sample locations" feature to GrProcessor

src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp

Index: src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp
diff --git a/src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp b/src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp
index 44db57e68d840067e7cd6da474b026bb60e84366..3fecff7b269be461e716acf28a619245cb308ce6 100644
--- a/src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp
+++ b/src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp
@@ -170,6 +170,11 @@ const char* GrGLSLFragmentShaderBuilder::fragmentPosition() {
     }
 }
 
+void GrGLSLFragmentShaderBuilder::appendSampleLocation(const char* sampleIdx) {
+    SkASSERT(fProgramBuilder->pipeline().hasSampleLocations());
+    this->codeAppendf("sampleLocations[%s]", sampleIdx);
+}
+
 void GrGLSLFragmentShaderBuilder::maskSampleCoverage(const char* mask, bool invert) {
     const GrGLSLCaps& glslCaps = *fProgramBuilder->glslCaps();
     if (!glslCaps.sampleVariablesSupport()) {
@@ -306,6 +311,22 @@ void GrGLSLFragmentShaderBuilder::onFinalize() {
     GrGLSLAppendDefaultFloatPrecisionDeclaration(kDefault_GrSLPrecision,
                                                  *fProgramBuilder->glslCaps(),
                                                  &this->precisionQualifier());
+    if (fProgramBuilder->pipeline().hasSampleLocations()) {
+        const GrPipeline& pipeline = fProgramBuilder->pipeline();
+        int effectiveSampleCnt = pipeline.effectiveSampleCount();
+        const SkPoint* sampleLocations = pipeline.getSampleLocations();
+        this->definitions().append("const ");
+        if (fProgramBuilder->glslCaps()->usesPrecisionModifiers()) {
+            this->definitions().append("highp ");
+        }
+        this->definitions().appendf("vec2 sampleLocations[] = vec2[](");
+        for (int i = 0; i < effectiveSampleCnt; ++i) {
+            this->definitions().appendf("vec2(%f, %f)%s",
+                                        sampleLocations[i].x(), sampleLocations[i].y(),
+                                        i + 1 != effectiveSampleCnt ? ", " : ");\n");
+        }
+        SkASSERT(fProgramBuilder->header().fSamplePatternKey == pipeline.getSamplePatternID());
+    }
 }
 
 void GrGLSLFragmentShaderBuilder::onBeforeChildProcEmitCode() {