GrGLInterface: Add support for NV_framebuffer_mixed_samples

Import glCoverageModulation if NV_framebuffer_mixed samples
is available

BUG=skia:3177

Review URL: https://codereview.chromium.org/993363002

include/gpu/gl/GrGLFunctions.h

@@ -259,6 +259,8 @@ extern "C" {
     // NV_path_rendering v1.3
     typedef GrGLvoid (GR_GL_FUNCTION_TYPE* GrGLProgramPathFragmentInputGenProc)(GrGLuint program, GrGLint location, GrGLenum genMode, GrGLint components,const GrGLfloat *coeffs);
     typedef GrGLenum (GR_GL_FUNCTION_TYPE* GrGLPathMemoryGlyphIndexArrayProc)(GrGLuint firstPathName, GrGLenum fontTarget, GrGLsizeiptr fontSize, const GrGLvoid *fontData, GrGLsizei faceIndex, GrGLuint firstGlyphIndex, GrGLsizei numGlyphs, GrGLuint pathParameterTemplate, GrGLfloat emScale);
+    // GL_NV_framebuffer_mixed_samples
+    typedef GrGLvoid (GR_GL_FUNCTION_TYPE* GrGLCoverageModulationProc)(GrGLenum components);
 }  // extern "C"
 
 #endif

include/gpu/gl/GrGLInterface.h

@@ -348,6 +348,8 @@ public:
         // NV_path_rendering v1.3
         GLPtr<GrGLProgramPathFragmentInputGenProc> fProgramPathFragmentInputGen;
         GLPtr<GrGLPathMemoryGlyphIndexArrayProc> fPathMemoryGlyphIndexArray;
+        // NV_framebuffer_mixed_samples
+        GLPtr<GrGLCoverageModulationProc> fCoverageModulation;
     } fFunctions;
 
     // Per-GL func callback

src/gpu/gl/GrGLAssembleInterface.cpp

@@ -278,6 +278,10 @@ const GrGLInterface* GrGLAssembleGLInterface(void* ctx, GrGLGetProc get) {
         GET_PROC_SUFFIX(PathMemoryGlyphIndexArray, NV);
     }
 
+    if (extensions.has("GL_NV_framebuffer_mixed_samples")) {
+        GET_PROC_SUFFIX(CoverageModulation, NV);
+    }
+
     if (extensions.has("GL_EXT_debug_marker")) {
         GET_PROC_SUFFIX(InsertEventMarker, EXT);
         GET_PROC_SUFFIX(PushGroupMarker, EXT);
@@ -519,6 +523,10 @@ const GrGLInterface* GrGLAssembleGLESInterface(void* ctx, GrGLGetProc get) {
         GET_PROC_SUFFIX(PathMemoryGlyphIndexArray, NV);
     }
 
+    if (extensions.has("GL_NV_framebuffer_mixed_samples")) {
+        GET_PROC_SUFFIX(CoverageModulation, NV);
+    }
+
     interface->fStandard = kGLES_GrGLStandard;
     interface->fExtensions.swap(&extensions);
 

src/gpu/gl/GrGLCaps.cpp

@@ -54,6 +54,7 @@ void GrGLCaps::reset() {
     fFBFetchNeedsCustomOutput = false;
     fFBFetchColorName = NULL;
     fFBFetchExtensionString = NULL;
+    fFBMixedSamplesSupport = false;
 
     fReadPixelsSupportedCache.reset();
 }
@@ -99,6 +100,7 @@ GrGLCaps& GrGLCaps::operator= (const GrGLCaps& caps) {
     fFBFetchNeedsCustomOutput = caps.fFBFetchNeedsCustomOutput;
     fFBFetchColorName = caps.fFBFetchColorName;
     fFBFetchExtensionString = caps.fFBFetchExtensionString;
+    fFBMixedSamplesSupport = caps.fFBMixedSamplesSupport;
 
     return *this;
 }
@@ -371,6 +373,8 @@ bool GrGLCaps::init(const GrGLContextInfo& ctxInfo, const GrGLInterface* gli) {
         fNvprSupport = kNone_NvprSupport;
     }
 
+    fFBMixedSamplesSupport = ctxInfo.hasExtension("GL_NV_framebuffer_mixed_samples");
+
     fGpuTracingSupport = ctxInfo.hasExtension("GL_EXT_debug_marker");
 
     // For now these two are equivalent but we could have dst read in shader via some other method

src/gpu/gl/GrGLCaps.h

@@ -178,6 +178,8 @@ public:
 
     const char* fbFetchExtensionString() const { return fFBFetchExtensionString; }
 
+    bool fbMixedSamplesSupport() const { return fFBMixedSamplesSupport; }
+
     InvalidateFBType invalidateFBType() const { return fInvalidateFBType; }
 
     /// What type of buffer mapping is supported?
@@ -389,6 +391,7 @@ private:
     bool fDropsTileOnZeroDivide : 1;
     bool fFBFetchSupport : 1;
     bool fFBFetchNeedsCustomOutput : 1;
+    bool fFBMixedSamplesSupport : 1;
 
     const char* fFBFetchColorName;
     const char* fFBFetchExtensionString;

src/gpu/gl/GrGLInterface.cpp

@@ -505,5 +505,11 @@ bool GrGLInterface::validate() const {
         }
     }
 
+    if (fExtensions.has("GL_NV_framebuffer_mixed_samples")) {
+        if (NULL == fFunctions.fCoverageModulation) {
+            RETURN_FALSE_INTERFACE
+        }
+    }
+
     return true;
 }