On gpu, use max(r,g,b) for coverage alpha in LCD and update lcd blend gm.

src/gpu/GrTextContext.cpp

 /*
  * Copyright 2010 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrTextContext.h"
 #include "GrBlurUtils.h"
 #include "GrContext.h"
@@ skipping 61 matching lines @@
         }
         textContext = textContext->fFallbackTextContext;
     } while (textContext);
 
     // fall back to drawing as a path
     this->drawPosTextAsPath(dc, rt, clip, skPaint, viewMatrix, text, byteLength, pos,
                             scalarsPerPosition, offset, clipBounds);
 }
 
 bool GrTextContext::ShouldDisableLCD(const SkPaint& paint) {
-    if (paint.getShader() ||
-        !SkXfermode::AsMode(paint.getXfermode(), nullptr) ||
+    if (!SkXfermode::AsMode(paint.getXfermode(), nullptr) ||
         paint.getMaskFilter() ||
         paint.getRasterizer() ||
-        paint.getColorFilter() ||
         paint.getPathEffect() ||
         paint.isFakeBoldText() ||
         paint.getStyle() != SkPaint::kFill_Style)
     {
         return true;
     }
     return false;
 }
 
 uint32_t GrTextContext::FilterTextFlags(const SkSurfaceProps& surfaceProps, const SkPaint& paint) {
@@ skipping 174 matching lines @@
     if (cache->getAuxProcData(GlyphCacheAuxProc, &auxData)) {
         scaler = (GrFontScaler*)auxData;
     }
     if (nullptr == scaler) {
         scaler = new GrFontScaler(cache);
         cache->setAuxProc(GlyphCacheAuxProc, scaler);
     }
 
     return scaler;
 }