GrGLInterface: Add support for NV_framebuffer_mixed_samples

src/gpu/gl/GrGLCaps.cpp

Index: src/gpu/gl/GrGLCaps.cpp
diff --git a/src/gpu/gl/GrGLCaps.cpp b/src/gpu/gl/GrGLCaps.cpp
index c9009b905362eb02ce9534af794610ebfe979294..fe52a540c6285a8637f1b5a540470592fc764b08 100644
--- a/src/gpu/gl/GrGLCaps.cpp
+++ b/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