Make ANGLE perf decisions be runtime rather than compile time

src/gpu/gl/GrGLCaps.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "GrGLCaps.h"
 
@@ skipping 32 matching lines @@
     fInstancedDrawingSupport = false;
     fDirectStateAccessSupport = false;
     fDebugSupport = false;
     fES2CompatibilitySupport = false;
     fMultisampleDisableSupport = false;
     fUseNonVBOVertexAndIndexDynamicData = false;
     fIsCoreProfile = false;
     fFullClearIsFree = false;
     fBindFragDataLocationSupport = false;
     fSRGBWriteControl = false;
+    fRGBA8888PixelsOpsAreSlow = false;
+    fPartialFBOReadIsSlow = false;
 
     fReadPixelsSupportedCache.reset();
 
     fShaderCaps.reset(SkNEW_ARGS(GrGLSLCaps, (contextOptions)));
 
     this->init(contextOptions, ctxInfo, glInterface);
 }
 
 void GrGLCaps::init(const GrContextOptions& contextOptions,
                     const GrGLContextInfo& ctxInfo,
@@ skipping 234 matching lines @@
     if (kGL_GrGLStandard == standard) {
         if (version >= GR_GL_VER(3, 0)) {
             fBindFragDataLocationSupport = true;
         }
     } else {
         if (version >= GR_GL_VER(3, 0) && ctxInfo.hasExtension("GL_EXT_blend_func_extended")) {
             fBindFragDataLocationSupport = true;
         }
     }
 
+#ifdef SK_BUILD_FOR_WIN
+    // We're assuming that on Windows Chromium we're using ANGLE.
+    bool isANGLE = kANGLE_GrGLDriver == ctxInfo.driver() ||
+                   kChromium_GrGLDriver == ctxInfo.driver();
+    // Angle has slow read/write pixel paths for 32bit RGBA (but fast for BGRA). 
+    fRGBA8888PixelsOpsAreSlow = isANGLE;
+    // On DX9 ANGLE reading a partial FBO is slow. TODO: Check whether this is still true and
+    // check DX11 ANGLE.
+    fPartialFBOReadIsSlow = isANGLE;
+#endif
+
     /**************************************************************************
     * GrShaderCaps fields
     **************************************************************************/
 
     glslCaps->fPathRenderingSupport = this->hasPathRenderingSupport(ctxInfo, gli);
 
     // For now these two are equivalent but we could have dst read in shader via some other method
     glslCaps->fDstReadInShaderSupport = glslCaps->fFBFetchSupport;
 
     // Enable supported shader-related caps
@@ skipping 808 matching lines @@
              (fFragCoordsConventionSupport ? "YES": "NO"));
     r.appendf("Vertex array object support: %s\n", (fVertexArrayObjectSupport ? "YES": "NO"));
     r.appendf("Instanced drawing support: %s\n", (fInstancedDrawingSupport ? "YES": "NO"));
     r.appendf("Direct state access support: %s\n", (fDirectStateAccessSupport ? "YES": "NO"));
     r.appendf("Debug support: %s\n", (fDebugSupport ? "YES": "NO"));
     r.appendf("Multisample disable support: %s\n", (fMultisampleDisableSupport ? "YES" : "NO"));
     r.appendf("Use non-VBO for dynamic data: %s\n",
              (fUseNonVBOVertexAndIndexDynamicData ? "YES" : "NO"));
     r.appendf("Full screen clear is free: %s\n", (fFullClearIsFree ? "YES" : "NO"));
     r.appendf("SRGB write contol: %s\n", (fSRGBWriteControl ? "YES" : "NO"));
+    r.appendf("RGBA 8888 pixel ops are slow: %s\n", (fRGBA8888PixelsOpsAreSlow? "YES" : "NO"));
+    r.appendf("Partial FBO read is slow: %s\n", (fPartialFBOReadIsSlow? "YES" : "NO"));
     return r;
 }
 
 static GrGLenum precision_to_gl_float_type(GrSLPrecision p) {
     switch (p) {
     case kLow_GrSLPrecision:
         return GR_GL_LOW_FLOAT;
     case kMedium_GrSLPrecision:
         return GR_GL_MEDIUM_FLOAT;
     case kHigh_GrSLPrecision:
@@ skipping 70 matching lines @@
         for (int p = 0; p < kGrSLPrecisionCount; ++p) {
             glslCaps->fFloatPrecisions[kGeometry_GrShaderType][p] = 
                                                glslCaps->fFloatPrecisions[kVertex_GrShaderType][p];
         }
     }
 }