Initial change to create GeometryProcessor

BUG=skia:
R=bsalomon@google.com, robertphillips@google.com, egdaniel@google.com, jvanverth@google.com

Author: joshualitt@chromium.org

Review URL: https://codereview.chromium.org/509153002
diff --git a/src/gpu/GrBitmapTextContext.cpp b/src/gpu/GrBitmapTextContext.cpp
index 6599d4e..ac4c078 100755
--- a/src/gpu/GrBitmapTextContext.cpp
+++ b/src/gpu/GrBitmapTextContext.cpp
@@ -108,7 +108,7 @@
         // This effect could be stored with one of the cache objects (atlas?)
         int coordsIdx = drawState->hasColorVertexAttribute() ? kGlyphCoordsWithColorAttributeIndex :
                                                                kGlyphCoordsNoColorAttributeIndex;
-        drawState->addCoverageEffect(fCachedEffect.get(), coordsIdx);
+        drawState->setGeometryProcessor(fCachedEffect.get(), coordsIdx);
         SkASSERT(NULL != fStrike);
         switch (fStrike->getMaskFormat()) {
             // Color bitmap text