Update PDF backend to support fallback fonts on Android.

include/ports/SkTypeface_android.h

Index: include/ports/SkTypeface_android.h
diff --git a/include/ports/SkTypeface_android.h b/include/ports/SkTypeface_android.h
index 1ee923c4e66b7f62073e18b2ed1d60c8d3330755..2166e08394a66cd11aa3210e0e93e5902f5a9b45 100644
--- a/include/ports/SkTypeface_android.h
+++ b/include/ports/SkTypeface_android.h
@@ -68,6 +68,22 @@ SK_API void SkUseTestFontConfigFile(const char* mainconf, const char* fallbackco
 SkTypeface* SkAndroidNextLogicalTypeface(SkFontID currFontID, SkFontID origFontID,
                                          const SkPaintOptionsAndroid& options);
 
+/**
+ * Given a glyphID (built using fallback font chaining) and its origin typeface
+ * return the actual typeface within the fallback chain that this glyphID
+ * resolves to. If no suitable typeface is found then NULL is returned. However,
+ * if returned typeface is not NULL it is assumed to be globally cached so the
+ * caller need not ref it.
+ *
+ * Optionally, if lower/upper bound params are provided and the returned
+ * typeface is not NULL, then these params are populated with the range of
+ * glyphIDs that this typeface is capable of resolving. The lower bound is
+ * inclusive while the upper bound is exclusive.
+ */
+SkTypeface* SkGetTypefaceForGlyphID(uint16_t glyphID, const SkTypeface* origTypeface,
+                                    const SkPaintOptionsAndroid& options,
+                                    int* lowerBounds = NULL, int* upperBounds = NULL);
+
 #endif // #ifdef SK_BUILD_FOR_ANDROID
 #ifdef SK_BUILD_FOR_ANDROID_FRAMEWORK