Differentiate maxColorSamples and maxStencilSamples in GrCaps

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1592803002

Review URL: https://codereview.chromium.org/1592803002
diff --git a/src/gpu/GrCaps.cpp b/src/gpu/GrCaps.cpp
index 101d5f4..f4c64c3 100644
--- a/src/gpu/GrCaps.cpp
+++ b/src/gpu/GrCaps.cpp
@@ -90,7 +90,7 @@
     fCompressedTexSubImageSupport = false;
     fOversizedStencilSupport = false;
     fTextureBarrierSupport = false;
-    fMixedSamplesSupport = false;
+    fUsesMixedSamples = false;
     fSupportsInstancedDraws = false;
     fFullClearIsFree = false;
     fMustClearUploadedBufferData = false;
@@ -104,7 +104,8 @@
 
     fMaxRenderTargetSize = 1;
     fMaxTextureSize = 1;
-    fMaxSampleCount = 0;
+    fMaxColorSampleCount = 0;
+    fMaxStencilSampleCount = 0;
 
     fSuppressPrints = options.fSuppressPrints;
     fImmediateFlush = options.fImmediateMode;
@@ -160,7 +161,7 @@
     r.appendf("Compressed Update Support          : %s\n", gNY[fCompressedTexSubImageSupport]);
     r.appendf("Oversized Stencil Support          : %s\n", gNY[fOversizedStencilSupport]);
     r.appendf("Texture Barrier Support            : %s\n", gNY[fTextureBarrierSupport]);
-    r.appendf("Mixed Samples Support              : %s\n", gNY[fMixedSamplesSupport]);
+    r.appendf("Uses Mixed Samples                 : %s\n", gNY[fUsesMixedSamples]);
     r.appendf("Supports instanced draws           : %s\n", gNY[fSupportsInstancedDraws]);
     r.appendf("Full screen clear is free          : %s\n", gNY[fFullClearIsFree]);
     r.appendf("Must clear buffer memory           : %s\n", gNY[fMustClearUploadedBufferData]);
@@ -175,7 +176,8 @@
 
     r.appendf("Max Texture Size                   : %d\n", fMaxTextureSize);
     r.appendf("Max Render Target Size             : %d\n", fMaxRenderTargetSize);
-    r.appendf("Max Sample Count                   : %d\n", fMaxSampleCount);
+    r.appendf("Max Color Sample Count             : %d\n", fMaxColorSampleCount);
+    r.appendf("Max Stencil Sample Count           : %d\n", fMaxStencilSampleCount);
 
     static const char* kBlendEquationSupportNames[] = {
         "Basic",