Asynchronously pre-fault the native library pages.

base/android/java/src/org/chromium/base/library_loader/LibraryLoader.java

Index: base/android/java/src/org/chromium/base/library_loader/LibraryLoader.java
diff --git a/base/android/java/src/org/chromium/base/library_loader/LibraryLoader.java b/base/android/java/src/org/chromium/base/library_loader/LibraryLoader.java
index d68fb4a814a19f1e187fd0afe77a2227b5df40e4..d3568bee8eb9c7bf77dc18fd28cefb50cb9216f4 100644
--- a/base/android/java/src/org/chromium/base/library_loader/LibraryLoader.java
+++ b/base/android/java/src/org/chromium/base/library_loader/LibraryLoader.java
@@ -5,6 +5,8 @@
 package org.chromium.base.library_loader;
 
 import android.content.Context;
+import android.content.pm.ApplicationInfo;
+import android.os.AsyncTask;
 import android.os.SystemClock;
 import android.util.Log;
 
@@ -13,6 +15,8 @@ import org.chromium.base.CommandLine;
 import org.chromium.base.JNINamespace;
 import org.chromium.base.TraceEvent;
 
+import java.io.File;
+import java.util.HashMap;
 import java.util.Locale;
 
 import javax.annotation.Nullable;
@@ -83,6 +87,9 @@ public class LibraryLoader {
     // The type of process the shared library is loaded in.
     private int mLibraryProcessType;
 
+    // Library -> Location it has been loaded from.
+    private HashMap<String, String> mLoadedFrom;
+
     /**
      * @param libraryProcessType the process the shared library is loaded in. refer to
      *                           LibraryProcessType for possible values.
@@ -102,6 +109,53 @@ public class LibraryLoader {
 
     private LibraryLoader(int libraryProcessType) {
         mLibraryProcessType = libraryProcessType;
+        mLoadedFrom = new HashMap<String, String>();
+    }
+
+    private void prefaultLibrary(final Context context, String library) {
+        ApplicationInfo applicationInfo = context.getApplicationInfo();
+        String apkFilePath = context.getApplicationInfo().sourceDir;
+
+        String pathToLibrary = mLoadedFrom.get(library);
+
+        if (pathToLibrary == null) {
+            Log.w(TAG, "Tried to find " + library + " before its load");
+            return;
+        }
+        long tick = SystemClock.elapsedRealtime();
+        boolean ok;
+        if (pathToLibrary.equals(apkFilePath)) {
+            ok = Linker.nativePrefaultLibraryInZipFile(apkFilePath, library);
+        } else {
+            ok = Linker.nativePrefaultLibraryInFile(pathToLibrary);
+        }
+        if (!ok) {
+            Log.w(TAG, "Error while prefaulting the native library " + pathToLibrary);
+            return;
+        }
+        long tock = SystemClock.elapsedRealtime();
+        Log.w(TAG, "Touching the native library " + library + " took "
+                + String.valueOf(tock - tick) + "ms");
+    }
+
+    /**
+     * Asynchronously pre-faults the pages from the native library.
+     *
+     * @param context The application context
+     */
+    public void asyncPrefaultLibraries(final Context context) {
+        new AsyncTask<Void, Void, Void>() {
+            @Override
+                protected Void doInBackground(Void... params) {
+                for (String library : NativeLibraries.LIBRARIES) {
+                    if (Linker.isChromiumLinkerLibrary(library)) {
+                        continue;
+                    }
+                    prefaultLibrary(context, library);
+                }
+                return null;
+            }
+        }.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
     }
 
     /**
@@ -261,6 +315,7 @@ public class LibraryLoader {
                                                 ? "using no map executable support fallback"
                                                 : "directly")
                                         + " from within " + apkFilePath);
+                                mLoadedFrom.put(library, apkFilePath);
                             } else {
                                 // Unpack library fallback.
                                 Log.i(TAG, "Loading " + library
@@ -270,10 +325,14 @@ public class LibraryLoader {
                                         context, library);
                                 fallbackWasUsed = true;
                                 Log.i(TAG, "Built fallback library " + libFilePath);
+                                mLoadedFrom.put(library, libFilePath);
                             }
                         } else {
                             // The library is in its own file.
                             Log.i(TAG, "Loading " + library);
+                            final ApplicationInfo applicationInfo = context.getApplicationInfo();
+                            mLoadedFrom.put(library, new File(applicationInfo.nativeLibraryDir,
+                                                              libFilePath).getAbsolutePath());
                         }
 
                         // Load the library.