Convert from glyph count to byte length

Canvas drawText* APIs are inconsistent, and this mismatch snuck through
our tests.

BUG=skia:3636
R=djsollen@google.com

Change-Id: Ibaab512c3f19df8445d582633b2748f1ec4d2902
diff --git a/libs/hwui/SkiaCanvas.cpp b/libs/hwui/SkiaCanvas.cpp
index 71088b7..8b11757 100644
--- a/libs/hwui/SkiaCanvas.cpp
+++ b/libs/hwui/SkiaCanvas.cpp
@@ -709,7 +709,7 @@
 
 void SkiaCanvas::drawTextOnPath(const uint16_t* glyphs, int count, const SkPath& path,
         float hOffset, float vOffset, const SkPaint& paint) {
-    mCanvas->drawTextOnPathHV(glyphs, count, path, hOffset, vOffset, paint);
+    mCanvas->drawTextOnPathHV(glyphs, count << 1, path, hOffset, vOffset, paint);
 }
 
 } // namespace android