Remove use of private SkBlurMask.h

This also makes a use of src/core/SkTraceEventCommon.h explicit.

These are small steps toward removing Skia's src/core from
the hwui include search path.

Change-Id: I4fe843a4e44a675748bfe2cef329202eb4dab7bf
Bug: skia:13983
diff --git a/libs/hwui/Properties.cpp b/libs/hwui/Properties.cpp
index b0896da..33c9eac 100644
--- a/libs/hwui/Properties.cpp
+++ b/libs/hwui/Properties.cpp
@@ -21,7 +21,7 @@
 #ifdef __ANDROID__
 #include "HWUIProperties.sysprop.h"
 #endif
-#include "SkTraceEventCommon.h"
+#include "src/core/SkTraceEventCommon.h"
 
 #include <algorithm>
 #include <cstdlib>