[Android] Refactor browser test execution.

testing/android/native_test/java/src/org/chromium/native_test/NativeBrowserTestActivity.java

Index: testing/android/native_test/java/src/org/chromium/native_test/NativeBrowserTestActivity.java
diff --git a/testing/android/native_test/java/src/org/chromium/native_test/NativeBrowserTestActivity.java b/testing/android/native_test/java/src/org/chromium/native_test/NativeBrowserTestActivity.java
index ac2ddeef84a6dbca5b71775ae60e536965f2757c..0f6628a648c7e71395a4a4207529dc7cb952062a 100644
--- a/testing/android/native_test/java/src/org/chromium/native_test/NativeBrowserTestActivity.java
+++ b/testing/android/native_test/java/src/org/chromium/native_test/NativeBrowserTestActivity.java
@@ -6,11 +6,17 @@ package org.chromium.native_test;
 
 import android.os.Bundle;
 
+import org.chromium.base.Log;
+
+import java.io.File;
+
 /**
  * An {@link android.app.Activity} for running native browser tests.
  */
 public abstract class NativeBrowserTestActivity extends NativeTestActivity {
 
+    private static final String TAG = "cr.native_test";
+
     private static final String BROWSER_TESTS_FLAGS[] = {
         // content::kSingleProcessTestsFlag
         "--single_process",
@@ -32,15 +38,48 @@ public abstract class NativeBrowserTestActivity extends NativeTestActivity {
 
     @Override
     public void onStart() {
+        deletePrivateDataDirectory();
         initializeBrowserProcess();
         super.onStart();
     }
 
+    /** Deletes a file or directory along with any of its children.
+     *
+     *  Note that, like File.delete(), this returns false if the file or directory couldn't be
+     *  fully deleted. This means that, in the directory case, some files may be deleted even if
+     *  the entire directory couldn't be.
+     *
+     *  @param file The file or directory to delete.
+     *  @return Whether or not the file or directory was deleted.
+     */
+    private static boolean deleteRecursive(File file) {
+        if (file == null) return true;
+
+        File[] children = file.listFiles();
+        if (children != null) {
+            for (File child : children) {
+                if (!deleteRecursive(child)) {
+                    return false;
+                }
+            }
+        }
+        return file.delete();
+    }
+
+    private void deletePrivateDataDirectory() {
+        File privateDataDirectory = getPrivateDataDirectory();
+        if (!deleteRecursive(privateDataDirectory)) {
+            Log.e(TAG, "Failed to remove %s", privateDataDirectory.getAbsolutePath());
+        }
+    }
+
+    /** Returns the test suite's private data directory. */
+    protected abstract File getPrivateDataDirectory();
+
     /** Initializes the browser process.
      *
      *  This generally includes loading native libraries and switching to the native command line,
      *  among other things.
      */
     protected abstract void initializeBrowserProcess();
-
 }