Add CPU backing store for GrAtlas to reduce texture uploads

src/gpu/GrDistanceFieldTextContext.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrDistanceFieldTextContext.h"
 #include "GrAtlas.h"
 #include "GrDrawTarget.h"
@@ skipping 83 matching lines @@
 void GrDistanceFieldTextContext::flushGlyphs() {
     if (NULL == fDrawTarget) {
         return;
     }
 
     GrDrawState* drawState = fDrawTarget->drawState();
     GrDrawState::AutoRestoreEffects are(drawState);
     drawState->setFromPaint(fPaint, fContext->getMatrix(), fContext->getRenderTarget());
 
     if (fCurrVertex > 0) {
+        fContext->getFontCache()->updateTextures();
+
         // setup our sampler state for our text texture/atlas
         SkASSERT(SkIsAlign4(fCurrVertex));
         SkASSERT(fCurrTexture);
         GrTextureParams params(SkShader::kRepeat_TileMode, GrTextureParams::kBilerp_FilterMode);
 
         // Effects could be stored with one of the cache objects (atlas?)
         if (fUseLCDText) {
             bool useBGR = SkDeviceProperties::Geometry::kBGR_Layout ==
                                                             fDeviceProperties.fGeometry.getLayout();
             drawState->addCoverageEffect(GrDistanceFieldLCDTextureEffect::Create(
@@ skipping 381 matching lines @@
                                       SkScalarToFixed(y) - (glyph.fAdvanceY >> alignShift)
                                         + SK_FixedHalf, //d1g.fHalfSampleY,
                                       fontScaler);
             }
             pos += scalarsPerPosition;
         }
     }
 
     this->finish();
 }