Revert to enabling all of -O2 as it exposes a bug in the toolchain.

gm/tilemodes_scaled.cpp

Index: gm/tilemodes_scaled.cpp
diff --git a/gm/tilemodes_scaled.cpp b/gm/tilemodes_scaled.cpp
index 360539ca499a6d512a2d23888def116d7874eaa4..28c106592a1674c77fc132ab77267c3a7125ea87 100644
--- a/gm/tilemodes_scaled.cpp
+++ b/gm/tilemodes_scaled.cpp
@@ -73,6 +73,13 @@ protected:
         return name;
     }
 
+#ifdef SK_CPU_ARM64
+    // Skip tiled drawing on 64-bit ARM until https://skbug.com/2908 is fixed.
+    virtual uint32_t onGetFlags() const SK_OVERRIDE {
+        return this->INHERITED::onGetFlags() | GM::kSkipTiled_Flag;
+    }
+#endif
+
     SkISize onISize() { return SkISize::Make(880, 760); }
 
     virtual void onOnceBeforeDraw() SK_OVERRIDE {