Express (GLSL expression, possibly known value) pairs as a class

src/gpu/gl/GrGLShaderBuilder.cpp

Index: src/gpu/gl/GrGLShaderBuilder.cpp
diff --git a/src/gpu/gl/GrGLShaderBuilder.cpp b/src/gpu/gl/GrGLShaderBuilder.cpp
index f4ffb4dd2ce2f071743c9c3d08b3edb7abaa4d56..e48295c91eafc489b0da5ff01e2eae7ec648f6cc 100644
--- a/src/gpu/gl/GrGLShaderBuilder.cpp
+++ b/src/gpu/gl/GrGLShaderBuilder.cpp
@@ -116,8 +116,6 @@ GrGLShaderBuilder::GrGLShaderBuilder(GrGpuGL* gpu,
     , fFSInputs(kVarsPerBlock)
     , fFSOutputs(kMaxFSOutputs)
     , fSetupFragPosition(false)
-    , fKnownColorValue(kNone_GrSLConstantVec)
-    , fKnownCoverageValue(kNone_GrSLConstantVec)
     , fHasCustomColorOutput(false)
     , fHasSecondaryOutput(false)
     , fTopLeftFragPosRead(kTopLeftFragPosRead_FragPosKey == desc.getHeader().fFragPosKey) {
@@ -180,10 +178,10 @@ GrGLShaderBuilder::GrGLShaderBuilder(GrGpuGL* gpu,
             break;
         }
         case GrGLProgramDesc::kTransBlack_ColorInput:
-            fKnownColorValue = kZeros_GrSLConstantVec;
+            fInputColor = GrGLSLExpr<4>(0);
             break;
         case GrGLProgramDesc::kSolidWhite_ColorInput:
-            fKnownColorValue = kOnes_GrSLConstantVec;
+            fInputColor = GrGLSLExpr<4>(1);
             break;
         default:
             GrCrash("Unknown color type.");
@@ -207,10 +205,10 @@ GrGLShaderBuilder::GrGLShaderBuilder(GrGpuGL* gpu,
             break;
         }
         case GrGLProgramDesc::kTransBlack_ColorInput:
-            fKnownCoverageValue = kZeros_GrSLConstantVec;
+            fInputCoverage = GrGLSLExpr<4>(0);
             break;
         case GrGLProgramDesc::kSolidWhite_ColorInput:
-            fKnownCoverageValue = kOnes_GrSLConstantVec;
+            fInputCoverage = GrGLSLExpr<4>(1);
             break;
         default:
             GrCrash("Unknown coverage type.");
@@ -344,7 +342,7 @@ void GrGLShaderBuilder::fsAppendTextureLookupAndModulate(
                                             GrSLType varyingType) {
     SkString lookup;
     this->appendTextureLookup(&lookup, sampler, coordName, varyingType);
-    GrGLSLModulatef<4>(&fFSCode, modulation, lookup.c_str());
+    fFSCode.append((GrGLSLExpr<4>(modulation) * GrGLSLExpr<4>(lookup)).c_str());
 }
 
 GrBackendEffectFactory::EffectKey GrGLShaderBuilder::KeyForTextureAccess(
@@ -561,14 +559,13 @@ void GrGLShaderBuilder::emitEffects(
                         const GrEffectStage* effectStages[],
                         const GrBackendEffectFactory::EffectKey effectKeys[],
                         int effectCnt,
-                        SkString* fsInOutColor,
-                        GrSLConstantVec* fsInOutColorKnownValue,
+                        GrGLSLExpr<4>* fsInOutColor,
                         SkTArray<GrGLUniformManager::UniformHandle, true>* effectSamplerHandles[],
                         GrGLEffect* glEffects[]) {
     bool effectEmitted = false;
 
-    SkString inColor = *fsInOutColor;
-    SkString outColor;
+    GrGLSLExpr<4> inColor = *fsInOutColor;
+    GrGLSLExpr<4> outColor;
 
     for (int e = 0; e < effectCnt; ++e) {
         SkASSERT(NULL != effectStages[e] && NULL != effectStages[e]->getEffect());
@@ -602,15 +599,19 @@ void GrGLShaderBuilder::emitEffects(
 
         glEffects[e] = effect->getFactory().createGLInstance(drawEffect);
 
-        if (kZeros_GrSLConstantVec == *fsInOutColorKnownValue) {
+        if (inColor.isZeros()) {
+            SkString inColorName;
             // Effects have no way to communicate zeros, they treat an empty string as ones.
-            this->nameVariable(&inColor, '\0', "input");
-            this->fsCodeAppendf("\tvec4 %s = %s;\n", inColor.c_str(), GrGLSLZerosVecf(4));
+            this->nameVariable(&inColorName, '\0', "input");
+            this->fsCodeAppendf("\tvec4 %s = %s;\n", inColorName.c_str(), inColor.c_str());
+            inColor = inColorName;
         }
 
         // create var to hold stage result
-        this->nameVariable(&outColor, '\0', "output");
-        this->fsCodeAppendf("\tvec4 %s;\n", outColor.c_str());
+        SkString outColorName;
+        this->nameVariable(&outColorName, '\0', "output");
+        this->fsCodeAppendf("\tvec4 %s;\n", outColorName.c_str());
+        outColor = outColorName;
 
         // Enclose custom code in a block to avoid namespace conflicts
         SkString openBrace;
@@ -624,7 +625,7 @@ void GrGLShaderBuilder::emitEffects(
                                drawEffect,
                                effectKeys[e],
                                outColor.c_str(),
-                               inColor.isEmpty() ? NULL : inColor.c_str(),
+                               inColor.isOnes() ? NULL : inColor.c_str(),
                                textureSamplers);
 
         if (NULL != fVertexBuilder.get()) {
@@ -633,7 +634,6 @@ void GrGLShaderBuilder::emitEffects(
         this->fsCodeAppend("\t}\n");
 
         inColor = outColor;
-        *fsInOutColorKnownValue = kNone_GrSLConstantVec;
         effectEmitted = true;
     }