Revert of Fix DexLoaderTest#testLoadAfterDeleteCachedDexes() flakiness

chrome/android/webapk/shell_apk/javatests/src/org/chromium/webapk/shell_apk/DexLoaderTest.java

Index: chrome/android/webapk/shell_apk/javatests/src/org/chromium/webapk/shell_apk/DexLoaderTest.java
diff --git a/chrome/android/webapk/shell_apk/javatests/src/org/chromium/webapk/shell_apk/DexLoaderTest.java b/chrome/android/webapk/shell_apk/javatests/src/org/chromium/webapk/shell_apk/DexLoaderTest.java
index a002a794c4696b6b739cc68e2a034825ca8d8c4f..1e77656b4ab66fced3d13a2deb9f8088f3a7bf47 100644
--- a/chrome/android/webapk/shell_apk/javatests/src/org/chromium/webapk/shell_apk/DexLoaderTest.java
+++ b/chrome/android/webapk/shell_apk/javatests/src/org/chromium/webapk/shell_apk/DexLoaderTest.java
@@ -42,18 +42,15 @@
             "org.chromium.webapk.shell_apk.test.dex_optimizer.DexOptimizerServiceImpl";
 
     /**
-     * Name of dex files in DexOptimizer.apk.
+     * Name of the dex file in DexOptimizer.apk.
      */
     private static final String DEX_ASSET_NAME = "canary.dex";
-    private static final String DEX_ASSET_NAME2 = "canary2.dex";
-
-    /**
-     * Classes to load to check whether dex is valid.
+
+    /**
+     * Class to load to check whether dex is valid.
      */
     private static final String CANARY_CLASS_NAME =
             "org.chromium.webapk.shell_apk.test.canary.Canary";
-    private static final String CANARY_CLASS_NAME2 =
-            "org.chromium.webapk.shell_apk.test.canary.Canary2";
 
     private Context mContext;
     private Context mRemoteContext;
@@ -220,33 +217,47 @@
     }
 
     /**
-     * Test loading a dex file from a directory which was previously used for loading a different
-     * dex file.
+     * Test that {@link DexLoader#load()} re-extracts the dex file from the APK after a call to
+     * {@link DexLoader#deleteCachedDexes()}.
      */
     @MediumTest
-    public void testLoadDifferentDexInLocalDataDir() {
+    public void testLoadAfterDeleteCachedDexes() {
         assertTrue(mLocalDexDir.mkdir());
 
-        // Load canary.dex
-        ClassLoader loader1 = DexLoader.load(
-                mRemoteContext, DEX_ASSET_NAME, CANARY_CLASS_NAME, null, mLocalDexDir);
-        assertNotNull(loader1);
-        assertTrue(canLoadCanaryClass(loader1));
-
-        File canaryDexFile1 = new File(mLocalDexDir, DEX_ASSET_NAME);
-        assertTrue(canaryDexFile1.exists());
+        {
+            // Load dex the first time. This should extract the dex file from the APK's assets and
+            // generate the optimized dex file.
+            FileMonitor localDexDirMonitor = new FileMonitor(mLocalDexDir);
+            localDexDirMonitor.startWatching();
+            ClassLoader loader = DexLoader.load(
+                    mRemoteContext, DEX_ASSET_NAME, CANARY_CLASS_NAME, null, mLocalDexDir);
+            localDexDirMonitor.stopWatching();
+
+            assertNotNull(loader);
+            assertTrue(canLoadCanaryClass(loader));
+
+            assertTrue(localDexDirMonitor.mReadPaths.contains(DEX_ASSET_NAME));
+            assertTrue(localDexDirMonitor.mModifiedPaths.contains(DEX_ASSET_NAME));
+        }
 
         DexLoader.deleteCachedDexes(mLocalDexDir);
 
-        ClassLoader loader2 = DexLoader.load(
-                mRemoteContext, DEX_ASSET_NAME2, CANARY_CLASS_NAME2, null, mLocalDexDir);
-        assertNotNull(loader2);
-        assertTrue(canLoadClass(loader2, CANARY_CLASS_NAME2));
-
-        // canary2.dex should have been extracted and the previously extracted canary.dex file
-        // should have been deleted.
-        assertTrue(new File(mLocalDexDir, DEX_ASSET_NAME2).exists());
-        assertFalse(canaryDexFile1.exists());
+        {
+            // Load dex a second time.
+            FileMonitor localDexDirMonitor = new FileMonitor(mLocalDexDir);
+            localDexDirMonitor.startWatching();
+            ClassLoader loader = DexLoader.load(
+                    mRemoteContext, DEX_ASSET_NAME, CANARY_CLASS_NAME, null, mLocalDexDir);
+            localDexDirMonitor.stopWatching();
+
+            // The returned ClassLoader should be valid.
+            assertNotNull(loader);
+            assertTrue(canLoadCanaryClass(loader));
+
+            // We should have re-extracted the dex from the APK's assets.
+            assertTrue(localDexDirMonitor.mReadPaths.contains(DEX_ASSET_NAME));
+            assertTrue(localDexDirMonitor.mModifiedPaths.contains(DEX_ASSET_NAME));
+        }
     }
 
     /**
@@ -314,13 +325,8 @@
 
     /** Returns whether the ClassLoader can load {@link CANARY_CLASS_NAME} */
     private boolean canLoadCanaryClass(ClassLoader loader) {
-        return canLoadClass(loader, CANARY_CLASS_NAME);
-    }
-
-    /** Returns whether the ClassLoader can load a class */
-    private boolean canLoadClass(ClassLoader loader, String className) {
-        try {
-            loader.loadClass(className);
+        try {
+            loader.loadClass(CANARY_CLASS_NAME);
             return true;
         } catch (Exception e) {
             return false;