Take only the scale params into account to rasterize text

This change extracts the scale parameters of the current transform
to pass then to the font renderer. Rotation and perspective are
applied to the generated mesh inside the vertex shader. This limits
the number of glyphs we have to create in the font cache and thus
reduces memory churn.

Change-Id: Ic5b3bae2b2b0e0250a8ee723b071a1709725c749
diff --git a/libs/hwui/LayerRenderer.cpp b/libs/hwui/LayerRenderer.cpp
index 14c7c39..9aa9615 100644
--- a/libs/hwui/LayerRenderer.cpp
+++ b/libs/hwui/LayerRenderer.cpp
@@ -92,11 +92,11 @@
     // who will invoke OpenGLRenderer::resume()
 }
 
-GLint LayerRenderer::getTargetFbo() {
+GLint LayerRenderer::getTargetFbo() const {
     return mLayer->getFbo();
 }
 
-bool LayerRenderer::suppressErrorChecks() {
+bool LayerRenderer::suppressErrorChecks() const {
     return true;
 }
 
@@ -104,7 +104,7 @@
 // Layer support
 ///////////////////////////////////////////////////////////////////////////////
 
-bool LayerRenderer::hasLayer() {
+bool LayerRenderer::hasLayer() const {
     return true;
 }
 
@@ -116,7 +116,7 @@
 // Dirty region tracking
 ///////////////////////////////////////////////////////////////////////////////
 
-Region* LayerRenderer::getRegion() {
+Region* LayerRenderer::getRegion() const {
     if (getSnapshot()->flags & Snapshot::kFlagFboTarget) {
         return OpenGLRenderer::getRegion();
     }