Avoid performing Android OMR1 dex compile workaround on local builds

The workaround causes perf regressions on the bots because it is
compiling the dex in the background. This is expected, so ignore the
workaround on local builds.

This also pushes compiling the dex to after startup in a best effort
task, to hopefully not compete with any crucial startup tasks and avoid
wiping any compiled dex before loading the chrome split.

Bug: 1160025, 1160029, 1159608
Change-Id: I704a3c3027ac13b7dc461a18bcc4e18f6e99c62d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2597890
Commit-Queue: Clark DuVall <cduvall@chromium.org>
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Auto-Submit: Clark DuVall <cduvall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#838505}

chrome/android/BUILD.gn

@@ -2196,6 +2196,7 @@ android_library("base_module_java") {
     "//chrome/browser/flags:java",
     "//chrome/browser/preferences:java",
     "//chrome/browser/util:java",
+    "//chrome/browser/version:java",
     "//components/crash/android:java",
     "//components/embedder_support/android:application_java",
     "//components/media_router/browser/android:cast_options_provider_java",

chrome/android/java/src/org/chromium/chrome/browser/base/SplitChromeApplication.java

@@ -25,8 +25,12 @@ import org.chromium.base.PackageUtils;
 import org.chromium.base.TraceEvent;
 import org.chromium.base.compat.ApiHelperForO;
 import org.chromium.base.metrics.RecordHistogram;
+import org.chromium.base.task.PostTask;
+import org.chromium.base.task.TaskTraits;
 import org.chromium.chrome.browser.preferences.ChromePreferenceKeys;
 import org.chromium.chrome.browser.preferences.SharedPreferencesManager;
+import org.chromium.chrome.browser.version.ChromeVersionInfo;
+import org.chromium.content_public.browser.BrowserStartupController;
 
 import java.lang.reflect.Field;
 
@@ -182,38 +186,59 @@ public class SplitChromeApplication extends SplitCompatApplication {
      * compile if necessary.
      */
     private void applyDexCompileWorkaround() {
-        // This bug only happens in OMR1.
-        if (Build.VERSION.SDK_INT != Build.VERSION_CODES.O_MR1) {
+        // This bug only happens in OMR1. Skip the workaround on local builds to avoid affecting
+        // perf bots.
+        if (Build.VERSION.SDK_INT != Build.VERSION_CODES.O_MR1
+                || ChromeVersionInfo.isLocalBuild()) {
             return;
         }
 
-        new Thread(() -> {
-            try {
-                // If the app has just been updated, it will be compiled with quicken. The next time
-                // bg-dexopt-job runs it will break the optimized dex for splits. If we force
-                // compile now, then bg-dexopt-job won't mess up the splits, and we save the user a
-                // slow startup.
-                if (needsDexCompileAfterUpdate()) {
-                    performDexCompile();
-                    return;
-                }
+        // Wait until startup completes so this doesn't slow down early startup or mess with
+        // compiled dex files before they get loaded initially.
+        // TODO(crbug.com/1159608): Determine if this works good enough, or if more needs to be done
+        // to avoid slowing startup.
+        BrowserStartupController.getInstance().addStartupCompletedObserver(
+                new BrowserStartupController.StartupCallback() {
+                    @Override
+                    public void onSuccess() {
+                        // BEST_EFFORT will only affect when the task runs, the dexopt will run with
+                        // normal priority (but in a separate process, due to using Runtime.exec()).
+                        PostTask.postTask(TaskTraits.BEST_EFFORT_MAY_BLOCK, () -> {
+                            try {
+                                // If the app has just been updated, it will be compiled with
+                                // quicken. The next time bg-dexopt-job runs it will break the
+                                // optimized dex for splits. If we force compile now, then
+                                // bg-dexopt-job won't mess up the splits, and we save the user a
+                                // slow startup.
+                                if (needsDexCompileAfterUpdate()) {
+                                    performDexCompile();
+                                    return;
+                                }
 
-                // Make sure all splits are compiled correclty, and if not force a compile.
-                String[] splitNames = ApiHelperForO.getSplitNames(getApplicationInfo());
-                for (int i = 0; i < splitNames.length; i++) {
-                    // Ignore config splits like "config.en".
-                    if (splitNames[i].contains(".")) {
-                        continue;
+                                // Make sure all splits are compiled correclty, and if not force a
+                                // compile.
+                                String[] splitNames =
+                                        ApiHelperForO.getSplitNames(getApplicationInfo());
+                                for (int i = 0; i < splitNames.length; i++) {
+                                    // Ignore config splits like "config.en".
+                                    if (splitNames[i].contains(".")) {
+                                        continue;
+                                    }
+                                    if (DexFile.isDexOptNeeded(
+                                                getApplicationInfo().splitSourceDirs[i])) {
+                                        performDexCompile();
+                                        return;
+                                    }
+                                }
+                            } catch (Exception e) {
+                                Log.e(TAG, "Error compiling dex.", e);
+                            }
+                        });
                     }
-                    if (DexFile.isDexOptNeeded(getApplicationInfo().splitSourceDirs[i])) {
-                        performDexCompile();
-                        return;
-                    }
-                }
-            } catch (Exception e) {
-                Log.e(TAG, "Error compiling dex.", e);
-            }
-        }).start();
+
+                    @Override
+                    public void onFailure() {}
+                });
     }
 
     /** Returns whether the dex has been compiled since the last app update. */