[WebLayer] Allow disk reads when creating PathClassLoader

PathClassLoader may call stat on the library paths, which causes a
strict mode violation. We may want to try to move this to a background
thread eventually.

Bug: 1071119
Change-Id: I51df3ee7bcd3a4bb94d4c0a56a21d97dc9406548
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2150886Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Clark DuVall <cduvall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#759398}

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

@@ -9,6 +9,7 @@ import android.content.pm.ApplicationInfo;
 import android.content.pm.PackageInfo;
 import android.content.pm.PackageManager;
 import android.os.Build;
+import android.os.StrictMode;
 import android.text.TextUtils;
 import android.util.Pair;
 
@@ -43,9 +44,18 @@ final class WebViewCompatibilityHelper {
                 libraryPaths[i] = "/." + libraryPaths[i];
             }
         }
-        ClassLoader classLoader = new PathClassLoader(getAllApkPaths(info.applicationInfo),
-                TextUtils.join(File.pathSeparator, libraryPaths),
-                ClassLoader.getSystemClassLoader());
+
+        // TODO(cduvall): PathClassLoader may call stat on the library paths, consider moving this
+        // to a background thread.
+        StrictMode.ThreadPolicy oldPolicy = StrictMode.allowThreadDiskReads();
+        ClassLoader classLoader;
+        try {
+            classLoader = new PathClassLoader(getAllApkPaths(info.applicationInfo),
+                    TextUtils.join(File.pathSeparator, libraryPaths),
+                    ClassLoader.getSystemClassLoader());
+        } finally {
+            StrictMode.setThreadPolicy(oldPolicy);
+        }
         return Pair.create(classLoader, WebLayer.WebViewCompatibilityResult.SUCCESS);
     }