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/media/libmedia/mediametadataretriever.cpp b/media/libmedia/mediametadataretriever.cpp
index e2712ba..39b5bc3 100644
--- a/media/libmedia/mediametadataretriever.cpp
+++ b/media/libmedia/mediametadataretriever.cpp
@@ -134,26 +134,15 @@
     return mRetriever->setMode(mode);
 }
 
-status_t MediaMetadataRetriever::getMode(int* mode)
+sp<IMemory> MediaMetadataRetriever::getFrameAtTime(int64_t timeUs, int option)
 {
-    LOGV("getMode");
-    Mutex::Autolock _l(mLock);
-    if (mRetriever == 0) {
-        LOGE("retriever is not initialized");
-        return INVALID_OPERATION;
-    }
-    return mRetriever->getMode(mode);
-}
-
-sp<IMemory> MediaMetadataRetriever::captureFrame()
-{
-    LOGV("captureFrame");
+    LOGV("getFrameAtTime: time(%lld us) option(%d)", timeUs, option);
     Mutex::Autolock _l(mLock);
     if (mRetriever == 0) {
         LOGE("retriever is not initialized");
         return NULL;
     }
-    return mRetriever->captureFrame();
+    return mRetriever->getFrameAtTime(timeUs, option);
 }
 
 const char* MediaMetadataRetriever::extractMetadata(int keyCode)