Make DisplayListRenderer inherit from Canvas, merge JNI

Incrementally unify the upper layers for Skia and HWUI.
Remove redundant code from GLES20Canvas.java; instead
use inherited mNativeCanvasWrapper and superclass method
definitions.

Moves some unrelated SkPaint utility functions from Renderer
to new utils/PaintUtils.

bug: 15672762
Change-Id: I4ddd4214b8e9eeb95289d054ef423f2542bb5fa5
diff --git a/libs/hwui/tests/main.cpp b/libs/hwui/tests/main.cpp
index ee16991..4efef6f 100644
--- a/libs/hwui/tests/main.cpp
+++ b/libs/hwui/tests/main.cpp
@@ -41,7 +41,7 @@
 static DisplayListRenderer* startRecording(RenderNode* node) {
     DisplayListRenderer* renderer = new DisplayListRenderer();
     renderer->setViewport(node->getWidth(), node->getHeight());
-    renderer->prepare(false);
+    renderer->prepare();
     return renderer;
 }