Android: Use synchronized methods for GameFileCache

Compared to the previous solution of using big `synchronized` blocks,
this makes GameFileCacheManager's executor thread release and re-lock
the lock when possible, giving the GUI thread a chance to do a
(comparatively) quick getOrAdd call if it needs to.

Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/model/GameFileCache.java

@@ -109,11 +109,11 @@ public class GameFileCache
 
   public static native String[] getAllGamePaths(String[] folderPaths, boolean recursiveScan);
 
-  public native int getSize();
+  public synchronized native int getSize();
 
-  public native GameFile[] getAllGames();
+  public synchronized native GameFile[] getAllGames();
 
-  public native GameFile addOrGet(String gamePath);
+  public synchronized native GameFile addOrGet(String gamePath);
 
   /**
    * Sets the list of games to cache.
@@ -123,7 +123,7 @@ public class GameFileCache
    *
    * @return true if the cache was modified
    */
-  public native boolean update(String[] gamePaths);
+  public synchronized native boolean update(String[] gamePaths);
 
   /**
    * For each game that already is in the cache, scans the folder that contains the game
@@ -131,9 +131,9 @@ public class GameFileCache
    *
    * @return true if the cache was modified
    */
-  public native boolean updateAdditionalMetadata();
+  public synchronized native boolean updateAdditionalMetadata();
 
-  public native boolean load();
+  public synchronized native boolean load();
 
-  public native boolean save();
+  public synchronized native boolean save();
 }

Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/services/GameFileCacheManager.java

@@ -158,7 +158,7 @@ public final class GameFileCacheManager
   {
     // Common case: The game is in the cache, so just grab it from there.
     // (Actually, addOrGet already checks for this case, but we want to avoid calling it if possible
-    // because onHandleIntent may hold a lock on sGameFileCache for extended periods of time.)
+    // because the executor thread may hold a lock on sGameFileCache for extended periods of time.)
     GameFile[] allGames = sGameFiles.getValue();
     for (GameFile game : allGames)
     {
@@ -171,10 +171,7 @@ public final class GameFileCacheManager
     // Unusual case: The game wasn't found in the cache.
     // Scan the game and add it to the cache so that we can return it.
     createGameFileCacheIfNeeded();
-    synchronized (sGameFileCache)
-    {
-      return sGameFileCache.addOrGet(gamePath);
-    }
+    return sGameFileCache.addOrGet(gamePath);
   }
 
   /**
@@ -186,14 +183,11 @@ public final class GameFileCacheManager
   {
     if (!sFirstLoadDone)
     {
-      synchronized (sGameFileCache)
+      sFirstLoadDone = true;
+      sGameFileCache.load();
+      if (sGameFileCache.getSize() != 0)
       {
-        sFirstLoadDone = true;
-        sGameFileCache.load();
-        if (sGameFileCache.getSize() != 0)
-        {
-          updateGameFileArray();
-        }
+        updateGameFileArray();
       }
     }
 
@@ -227,24 +221,21 @@ public final class GameFileCacheManager
     {
       String[] gamePaths = GameFileCache.getAllGamePaths();
 
-      synchronized (sGameFileCache)
+      boolean changed = sGameFileCache.update(gamePaths);
+      if (changed)
       {
-        boolean changed = sGameFileCache.update(gamePaths);
-        if (changed)
-        {
-          updateGameFileArray();
-        }
+        updateGameFileArray();
+      }
 
-        boolean additionalMetadataChanged = sGameFileCache.updateAdditionalMetadata();
-        if (additionalMetadataChanged)
-        {
-          updateGameFileArray();
-        }
+      boolean additionalMetadataChanged = sGameFileCache.updateAdditionalMetadata();
+      if (additionalMetadataChanged)
+      {
+        updateGameFileArray();
+      }
 
-        if (changed || additionalMetadataChanged)
-        {
-          sGameFileCache.save();
-        }
+      if (changed || additionalMetadataChanged)
+      {
+        sGameFileCache.save();
       }
     }