[WebLayer] Only load splits which are used by WebLayer

This should help startup on Monochrome since we can avoid loading splits
that will not be used by WebLayer. This will likely have memory benefits
in the field.

-4.4% weblayer_startup_wall_time:
https://pinpoint-dot-chromeperf.appspot.com/job/10843ff4d20000

Bug: 1146438
Change-Id: I1c1dfcda323e9f8c41d05959c580ce050f76bf0e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2626101Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Clark DuVall <cduvall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843363}

weblayer/public/java/org/chromium/weblayer/WebLayer.java

@@ -7,6 +7,7 @@ package org.chromium.weblayer;
 import android.annotation.TargetApi;
 import android.content.Context;
 import android.content.Intent;
+import android.content.pm.ApplicationInfo;
 import android.content.pm.PackageInfo;
 import android.content.pm.PackageManager;
 import android.os.Build;
@@ -802,9 +803,10 @@ public class WebLayer {
         }
     }
 
+    /** Utility class to use new APIs that were added in O (API level 26). */
     @VerifiesOnO
     @TargetApi(Build.VERSION_CODES.O)
-    private static final class ApiHelperForO {
+    /* package */ static final class ApiHelperForO {
         /** See {@link Context.createContextForSplit(String) }. */
         public static Context createContextForSplit(Context context, String name)
                 throws PackageManager.NameNotFoundException {
@@ -815,6 +817,11 @@ public class WebLayer {
                 StrictMode.setThreadPolicy(oldPolicy);
             }
         }
+
+        /** See {@link ApplicationInfo#splitNames}. */
+        public static String[] getSplitNames(ApplicationInfo info) {
+            return info.splitNames;
+        }
     }
 
     @VerifiesOnR

weblayer/public/java/org/chromium/weblayer/WebViewCompatibilityHelper.java

@@ -69,17 +69,31 @@ final class WebViewCompatibilityHelper {
     private static String getAllApkPaths(ApplicationInfo info) {
         // The OS version of this method also includes resourceDirs, but this is not available in
         // the SDK.
-        final String[][] inputLists = {info.sharedLibraryFiles, info.splitSourceDirs};
         final List<String> output = new ArrayList<>(10);
-        for (String[] inputList : inputLists) {
-            if (inputList != null) {
-                for (String input : inputList) {
-                    output.add(input);
+        // First add the base APK path, since this is always needed.
+        if (info.sourceDir != null) {
+            output.add(info.sourceDir);
+        }
+        // Next add split paths that are used by WebLayer.
+        if (info.splitSourceDirs != null) {
+            String[] splitNames = null;
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+                splitNames = WebLayer.ApiHelperForO.getSplitNames(info);
+            }
+            for (int i = 0; i < info.splitSourceDirs.length; i++) {
+                // WebLayer only uses the "chrome" and "weblayer" splits.
+                if (splitNames != null && !splitNames[i].equals("chrome")
+                        && !splitNames[i].equals("weblayer")) {
+                    continue;
                 }
+                output.add(info.splitSourceDirs[i]);
             }
         }
-        if (info.sourceDir != null) {
-            output.add(info.sourceDir);
+        // Last, add shared library paths.
+        if (info.sharedLibraryFiles != null) {
+            for (String input : info.sharedLibraryFiles) {
+                output.add(input);
+            }
         }
         return TextUtils.join(File.pathSeparator, output);
     }