Create swizzle table inside of glsl caps

src/gpu/gl/GrGLGpu.cpp

Index: src/gpu/gl/GrGLGpu.cpp
diff --git a/src/gpu/gl/GrGLGpu.cpp b/src/gpu/gl/GrGLGpu.cpp
index dc3ea0c3d782afd8afdd6e6172e395b08d87f180..6c47baf9d319858d96ed3ba4f90f3e80cfe7d1e1 100644
--- a/src/gpu/gl/GrGLGpu.cpp
+++ b/src/gpu/gl/GrGLGpu.cpp
@@ -2396,19 +2396,30 @@ static inline GrGLenum tile_to_gl_wrap(SkShader::TileMode tm) {
     return gWrapModes[tm];
 }
 
-const GrGLenum* GrGLGpu::GetTexParamSwizzle(GrPixelConfig config, const GrGLCaps& caps) {
-    if (caps.textureSwizzleSupport() && GrPixelConfigIsAlphaOnly(config)) {
-        if (caps.textureRedSupport()) {
-            static const GrGLenum gRedSmear[] = { GR_GL_RED, GR_GL_RED, GR_GL_RED, GR_GL_RED };
-            return gRedSmear;
-        } else {
-            static const GrGLenum gAlphaSmear[] = { GR_GL_ALPHA, GR_GL_ALPHA,
-                                                    GR_GL_ALPHA, GR_GL_ALPHA };
-            return gAlphaSmear;
-        }
-    } else {
-        static const GrGLenum gStraight[] = { GR_GL_RED, GR_GL_GREEN, GR_GL_BLUE, GR_GL_ALPHA };
-        return gStraight;
+static GrGLenum get_component_enum_from_char(char component) {
+    switch (component) {
+        case 'r':
+           return GR_GL_RED;
+        case 'g':
+           return GR_GL_GREEN;
+        case 'b':
+           return GR_GL_BLUE;
+        case 'a':
+           return GR_GL_ALPHA;
+        default:
+            SkFAIL("Unsupported component");
+            return 0;
+    }
+}
+
+/** If texture swizzling is available using tex parameters then it is preferred over mangling
+  the generated shader code. This potentially allows greater reuse of cached shaders. */
+static void get_tex_param_swizzle(GrPixelConfig config,
+                                  const GrGLSLCaps& caps,
+                                  GrGLenum* glSwizzle) {
+    const char* swizzle = caps.getSwizzleMap(config);
+    for (int i = 0; i < 4; ++i) {
+        glSwizzle[i] = get_component_enum_from_char(swizzle[i]);
     }
 }
 
@@ -2477,9 +2488,7 @@ void GrGLGpu::bindTexture(int unitIdx, const GrTextureParams& params, GrGLTextur
 
     newTexParams.fWrapS = tile_to_gl_wrap(params.getTileModeX());
     newTexParams.fWrapT = tile_to_gl_wrap(params.getTileModeY());
-    memcpy(newTexParams.fSwizzleRGBA,
-           GetTexParamSwizzle(texture->config(), this->glCaps()),
-           sizeof(newTexParams.fSwizzleRGBA));
+    get_tex_param_swizzle(texture->config(), *this->glCaps().glslCaps(), newTexParams.fSwizzleRGBA);
     if (setAll || newTexParams.fMagFilter != oldTexParams.fMagFilter) {
         this->setTextureUnit(unitIdx);
         GL_CALL(TexParameteri(target, GR_GL_TEXTURE_MAG_FILTER, newTexParams.fMagFilter));
@@ -2496,7 +2505,7 @@ void GrGLGpu::bindTexture(int unitIdx, const GrTextureParams& params, GrGLTextur
         this->setTextureUnit(unitIdx);
         GL_CALL(TexParameteri(target, GR_GL_TEXTURE_WRAP_T, newTexParams.fWrapT));
     }
-    if (this->glCaps().textureSwizzleSupport() &&
+    if (!this->glCaps().glslCaps()->mustSwizzleInShader() &&
         (setAll || memcmp(newTexParams.fSwizzleRGBA,
                           oldTexParams.fSwizzleRGBA,
                           sizeof(newTexParams.fSwizzleRGBA)))) {