Replace GrGLInterface's function pointers with std::functions

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 cb3f5dd55f7329503a97703a9cd25f9f9f9cf759..c2ace6cd368948d25d60f95b766895dcfd1ce740 100644
--- a/src/gpu/gl/GrGLCaps.cpp
+++ b/src/gpu/gl/GrGLCaps.cpp
@@ -669,11 +669,11 @@ bool GrGLCaps::hasPathRenderingSupport(const GrGLContextInfo& ctxInfo, const GrG
     // additions are detected by checking the existence of the function.
     // We also use *Then* functions that not all drivers might have. Check
     // them for consistency.
-    if (nullptr == gli->fFunctions.fStencilThenCoverFillPath ||
-        nullptr == gli->fFunctions.fStencilThenCoverStrokePath ||
-        nullptr == gli->fFunctions.fStencilThenCoverFillPathInstanced ||
-        nullptr == gli->fFunctions.fStencilThenCoverStrokePathInstanced ||
-        nullptr == gli->fFunctions.fProgramPathFragmentInputGen) {
+    if (!gli->fFunctions.fStencilThenCoverFillPath ||
+        !gli->fFunctions.fStencilThenCoverStrokePath ||
+        !gli->fFunctions.fStencilThenCoverFillPathInstanced ||
+        !gli->fFunctions.fStencilThenCoverStrokePathInstanced ||
+        !gli->fFunctions.fProgramPathFragmentInputGen) {
         return false;
     }
     return true;