Make DataSourceFactory singletone

This is preparation for having a subclass of DataSourceFactory which
is only used in mediaserver process with OMA (forward-lock) use case.

Test: build
Bug: 142567168
Change-Id: I2a1ab3d1ae89f657a84376d9a95d4e814b545b4f
diff --git a/media/libmediaplayerservice/nuplayer/GenericSource.cpp b/media/libmediaplayerservice/nuplayer/GenericSource.cpp
index e26f1e6..3a387e2 100644
--- a/media/libmediaplayerservice/nuplayer/GenericSource.cpp
+++ b/media/libmediaplayerservice/nuplayer/GenericSource.cpp
@@ -385,7 +385,7 @@
             if (!strncasecmp("http://", uri, 7) || !strncasecmp("https://", uri, 8)) {
                 sp<DataSource> httpSource;
                 mDisconnectLock.unlock();
-                httpSource = DataSourceFactory::CreateMediaHTTP(mHTTPService);
+                httpSource = DataSourceFactory::getInstance()->CreateMediaHTTP(mHTTPService);
                 if (httpSource == NULL) {
                     ALOGE("Failed to create http source!");
                     notifyPreparedAndCleanup(UNKNOWN_ERROR);
@@ -401,7 +401,7 @@
             mLock.unlock();
             mDisconnectLock.unlock();
             // This might take long time if connection has some issue.
-            sp<DataSource> dataSource = DataSourceFactory::CreateFromURI(
+            sp<DataSource> dataSource = DataSourceFactory::getInstance()->CreateFromURI(
                    mHTTPService, uri, &mUriHeaders, &contentType,
                    static_cast<HTTPBase *>(mHttpSource.get()));
             mDisconnectLock.lock();