Move Layer creation/deletion into the RenderPipeline.

Test: refactoring. existing tests still pass.
Change-Id: I032c33896a0cb74c91e2a913a584373518466b88
diff --git a/libs/hwui/renderthread/CanvasContext.cpp b/libs/hwui/renderthread/CanvasContext.cpp
index 43471e5..0f2d55b 100644
--- a/libs/hwui/renderthread/CanvasContext.cpp
+++ b/libs/hwui/renderthread/CanvasContext.cpp
@@ -85,6 +85,18 @@
     return nullptr;
 }
 
+void CanvasContext::destroyLayer(RenderNode* node) {
+    auto renderType = Properties::getRenderPipelineType();
+    switch (renderType) {
+        case RenderPipelineType::OpenGL:
+            OpenGLPipeline::destroyLayer(node);
+            break;
+        default:
+            LOG_ALWAYS_FATAL("canvas context type %d not supported", (int32_t) renderType);
+            break;
+    }
+}
+
 CanvasContext::CanvasContext(RenderThread& thread, bool translucent,
         RenderNode* rootRenderNode, IContextFactory* contextFactory,
         std::unique_ptr<IRenderPipeline> renderPipeline)