Unload CCT module when activity is destroyed.

Bug: 853732
Change-Id: I82029d1dd7067ab6d615b8cb77797f6edd5fe65a
Reviewed-on: https://chromium-review.googlesource.com/1113752
Commit-Queue: Michael van Ouwerkerk <mvanouwerkerk@chromium.org>
Reviewed-by: Bernhard Bauer <bauerb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#571084}

chrome/android/java/src/org/chromium/chrome/browser/customtabs/CustomTabActivity.java

@@ -823,6 +823,8 @@ public class CustomTabActivity extends ChromeActivity {
     protected void onDestroyInternal() {
         super.onDestroyInternal();
         if (mActivityDelegate != null) mActivityDelegate.onDestroy(isChangingConfigurations());
+        mConnection.maybeUnloadModule(mIntentDataProvider.getModulePackageName(),
+                mIntentDataProvider.getModuleClassName());
     }
 
     @Override

chrome/android/java/src/org/chromium/chrome/browser/customtabs/CustomTabsConnection.java

@@ -235,6 +235,7 @@ public class CustomTabsConnection {
 
     /** The module package name and class name. */
     private Pair<String, String> mModuleNames;
+    private int mModuleUseCount;
 
     /** The module entry point. */
     private ModuleEntryPoint mModuleEntryPoint;
@@ -1432,12 +1433,27 @@ public class CustomTabsConnection {
                     || !mModuleNames.second.equals(className))) {
                 throw new IllegalStateException("Only one module can be loaded at a time.");
             }
+            mModuleUseCount++;
             return mModuleEntryPoint;
         }
 
-        // TODO(https://crbug.com/853732): Add cleanup mechanism to unload the module.
         mModuleNames = new Pair<>(packageName, className);
         mModuleEntryPoint = ModuleLoader.loadModule(packageName, className);
+        if (mModuleEntryPoint != null) mModuleUseCount++;
         return mModuleEntryPoint;
     }
+
+    public void maybeUnloadModule(String packageName, String className) {
+        if (mModuleEntryPoint == null || mModuleNames == null) return;
+        if ((!mModuleNames.first.equals(packageName) || !mModuleNames.second.equals(className))) {
+            throw new IllegalStateException(
+                    "There is no module for package " + packageName + " and class " + className);
+        }
+        mModuleUseCount--;
+        if (mModuleUseCount == 0) {
+            mModuleEntryPoint.onDestroy();
+            mModuleEntryPoint = null;
+            mModuleNames = null;
+        }
+    }
 }