Prepare for publishing MediaMetadataRetriever as public API

step one:
o replaced captureFrame with getFrameAtTime
o removed getMode

bug - 2433195

Change-Id: I38a8cecef29014692f0b08b8818326e3ebb40a12
diff --git a/include/media/mediametadataretriever.h b/include/media/mediametadataretriever.h
index dbbcc49..ed54b37 100644
--- a/include/media/mediametadataretriever.h
+++ b/include/media/mediametadataretriever.h
@@ -81,8 +81,7 @@
     status_t setDataSource(const char* dataSourceUrl);
     status_t setDataSource(int fd, int64_t offset, int64_t length);
     status_t setMode(int mode);
-    status_t getMode(int* mode);
-    sp<IMemory> captureFrame();
+    sp<IMemory> getFrameAtTime(int64_t timeUs, int option);
     sp<IMemory> extractAlbumArt();
     const char* extractMetadata(int keyCode);