Export support types from extractors

Make each extractor  plugin export a list of file types it supports,
so we no longer need to hardcode such a list in the framework.

Test: manual
Change-Id: I1e41a5d477ea56960ad3e4bc35f5183c03c3fe3a
diff --git a/media/libmedia/IMediaExtractorService.cpp b/media/libmedia/IMediaExtractorService.cpp
index 0295abc..243b09d 100644
--- a/media/libmedia/IMediaExtractorService.cpp
+++ b/media/libmedia/IMediaExtractorService.cpp
@@ -29,6 +29,7 @@
 enum {
     MAKE_EXTRACTOR = IBinder::FIRST_CALL_TRANSACTION,
     MAKE_IDATA_SOURCE_FD,
+    GET_SUPPORTED_TYPES,
 };
 
 class BpMediaExtractorService : public BpInterface<IMediaExtractorService>
@@ -68,6 +69,24 @@
         }
         return nullptr;
     }
+
+    virtual std::unordered_set<std::string> getSupportedTypes() {
+        std::unordered_set<std::string> supportedTypes;
+        Parcel data, reply;
+        data.writeInterfaceToken(IMediaExtractorService::getInterfaceDescriptor());
+        status_t ret = remote()->transact(GET_SUPPORTED_TYPES, data, &reply);
+        if (ret == NO_ERROR) {
+            // process reply
+            while(true) {
+                const char *ext = reply.readCString();
+                if (!ext) {
+                    break;
+                }
+                supportedTypes.insert(std::string(ext));
+            }
+        }
+        return supportedTypes;
+    }
 };
 
 IMPLEMENT_META_INTERFACE(MediaExtractorService, "android.media.IMediaExtractorService");
@@ -113,6 +132,15 @@
             return NO_ERROR;
         }
 
+        case GET_SUPPORTED_TYPES:
+        {
+            CHECK_INTERFACE(IMediaExtractorService, data, reply);
+            std::unordered_set<std::string> supportedTypes = getSupportedTypes();
+            for (auto it = supportedTypes.begin(); it != supportedTypes.end(); ++it) {
+                reply->writeCString((*it).c_str());
+            }
+            return NO_ERROR;
+        }
         default:
             return BBinder::onTransact(code, data, reply, flags);
     }