Add CPU backing store for GrAtlas to reduce texture uploads

src/gpu/GrBitmapTextContext.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 "GrBitmapTextContext.h"
 #include "GrAtlas.h"
 #include "GrDrawTarget.h"
@@ skipping 50 matching lines @@
 void GrBitmapTextContext::flushGlyphs() {
     if (NULL == fDrawTarget) {
         return;
     }
 
     GrDrawState* drawState = fDrawTarget->drawState();
     GrDrawState::AutoRestoreEffects are(drawState);
     drawState->setFromPaint(fPaint, SkMatrix::I(), 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::kNone_FilterMode);
 
         // This effect could be stored with one of the cache objects (atlas?)
         drawState->addCoverageEffect(
                                 GrCustomCoordsTextureEffect::Create(fCurrTexture, params),
                                 kGlyphCoordsAttributeIndex)->unref();
 
@@ skipping 543 matching lines @@
 
     fVertices[2*fCurrVertex].setRectFan(r.fLeft, r.fTop, r.fRight, r.fBottom,
                                         2 * sizeof(SkPoint));
     fVertices[2*fCurrVertex+1].setRectFan(SkFixedToFloat(texture->normalizeFixedX(tx)),
                                           SkFixedToFloat(texture->normalizeFixedY(ty)),
                                           SkFixedToFloat(texture->normalizeFixedX(tx + width)),
                                           SkFixedToFloat(texture->normalizeFixedY(ty + height)),
                                           2 * sizeof(SkPoint));
     fCurrVertex += 4;
 }