--- a/mobile/android/app/lint.xml
+++ b/mobile/android/app/lint.xml
@@ -33,17 +33,16 @@
     <issue id="Instantiatable" severity="warning" />
     <issue id="LongLogTag" severity="warning" />
     <issue id="MissingPermission" severity="warning" />
     <issue id="OnClick" severity="warning" />
     <issue id="ReferenceType" severity="warning" />
     <issue id="ResourceAsColor" severity="warning" />
     <issue id="ResourceType" severity="warning" />
     <issue id="ValidFragment" severity="warning" />
-    <issue id="WrongConstant" severity="warning" />
 
     <!-- New Android-Gradle lint integration regressed this check. -->
     <issue id="MissingRegistered" severity="warning" />
 
     <!-- Fixes are in progress but we would like to block future candidates.
          The ** in the path are wildcards. We need these wildcards to not change our code structure.
          See: http://stackoverflow.com/questions/43994420/what-path-is-the-issue-ignore-path-element-in-lint-xml-relative-to -->
     <issue id="NewApi" severity="error">

--- a/mobile/android/base/java/org/mozilla/gecko/activitystream/ActivityStreamTelemetry.java
+++ b/mobile/android/base/java/org/mozilla/gecko/activitystream/ActivityStreamTelemetry.java
@@ -1,15 +1,16 @@
 /* -*- Mode: Java; c-basic-offset: 4; tab-width: 4; indent-tabs-mode: nil; -*-
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 package org.mozilla.gecko.activitystream;
 
+import android.annotation.SuppressLint;
 import android.content.Context;
 import android.content.SharedPreferences;
 import android.content.res.Resources;
 import android.support.annotation.NonNull;
 
 import org.json.JSONArray;
 import org.json.JSONException;
 import org.json.JSONObject;
@@ -211,18 +212,17 @@ public class ActivityStreamTelemetry {
                     case BrowserContract.TopSites.TYPE_SUGGESTED:
                         this.set(Contract.SOURCE_SUBTYPE, Contract.SUBTYPE_SUGGESTED);
                         break;
                     case BrowserContract.TopSites.TYPE_TOP:
                         this.set(Contract.SOURCE_SUBTYPE, Contract.SUBTYPE_TOP);
                         break;
                     // While we also have a "blank" type, it is not used by Activity Stream.
                     case BrowserContract.TopSites.TYPE_BLANK:
-                    default:
-                        throw new IllegalStateException("Unknown top site type: " + topSite.getType());
+                        throw new IllegalStateException("Unknown top site type :" + (int) topSite.getType());
                 }
 
                 return this;
             }
 
             public String build() {
                 return data.toString();
             }

--- a/mobile/android/base/java/org/mozilla/gecko/dlc/BaseAction.java
+++ b/mobile/android/base/java/org/mozilla/gecko/dlc/BaseAction.java
@@ -1,15 +1,16 @@
 /* -*- Mode: Java; c-basic-offset: 4; tab-width: 20; indent-tabs-mode: nil; -*-
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 package org.mozilla.gecko.dlc;
 
+import android.annotation.SuppressLint;
 import android.content.Context;
 import android.support.annotation.IntDef;
 import android.util.Log;
 
 import org.mozilla.gecko.AppConstants;
 import org.mozilla.gecko.background.nativecode.NativeCrypto;
 import org.mozilla.gecko.dlc.catalog.DownloadContent;
 import org.mozilla.gecko.dlc.catalog.DownloadContentCatalog;
@@ -95,17 +96,17 @@ public abstract class BaseAction {
     protected File getDestinationFile(Context context, DownloadContent content)
             throws UnrecoverableDownloadContentException, RecoverableDownloadContentException {
         File destinationDirectory;
         if (content.isFont()) {
             destinationDirectory = new File(context.getApplicationInfo().dataDir, "fonts");
         } else if (content.isHyphenationDictionary()) {
             destinationDirectory = new File(context.getApplicationInfo().dataDir, "hyphenation");
         } else {
-            throw new UnrecoverableDownloadContentException("Can't determine destination for kind: " + content.getKind());
+            throw new UnrecoverableDownloadContentException("Can't determine destination for kind: " + (String) content.getKind());
         }
 
         if (!destinationDirectory.exists() && !destinationDirectory.mkdirs()) {
             throw new RecoverableDownloadContentException(RecoverableDownloadContentException.DISK_IO,
                     "Destination directory does not exist and cannot be created");
         }
 
         return new File(destinationDirectory, content.getFilename());

--- a/mobile/android/base/java/org/mozilla/gecko/dlc/DownloadAction.java
+++ b/mobile/android/base/java/org/mozilla/gecko/dlc/DownloadAction.java
@@ -1,15 +1,16 @@
 /* -*- Mode: Java; c-basic-offset: 4; tab-width: 20; indent-tabs-mode: nil; -*-
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 package org.mozilla.gecko.dlc;
 
+import android.annotation.SuppressLint;
 import android.content.Context;
 import android.net.ConnectivityManager;
 import android.net.NetworkInfo;
 import android.support.v4.net.ConnectivityManagerCompat;
 import android.util.Log;
 
 import org.mozilla.gecko.dlc.catalog.DownloadContent;
 import org.mozilla.gecko.dlc.catalog.DownloadContentCatalog;
@@ -101,17 +102,17 @@ public class DownloadAction extends Base
                 if (!verify(temporaryFile, content.getDownloadChecksum())) {
                     Log.w(LOGTAG, "Wrong checksum after download, content=" + content.getId());
                     temporaryFile.delete();
                     DownloadContentTelemetry.eventDownloadFailure(content, DownloadContentTelemetry.ERROR_CHECKSUM);
                     continue;
                 }
 
                 if (!content.isAssetArchive()) {
-                    Log.e(LOGTAG, "Downloaded content is not of type 'asset-archive': " + content.getType());
+                    Log.e(LOGTAG, "Downloaded content is not of type 'asset-archive': " + (String) content.getType());
                     temporaryFile.delete();
                     DownloadContentTelemetry.eventDownloadFailure(content, DownloadContentTelemetry.ERROR_LOGIC);
                     continue;
                 }
 
                 extract(temporaryFile, destinationFile, content.getChecksum());
 
                 catalog.markAsDownloaded(content);

--- a/mobile/android/base/moz.build
+++ b/mobile/android/base/moz.build
@@ -1155,17 +1155,17 @@ if CONFIG['MOZ_INSTALL_TRACKING']:
 gbjar.extra_jars += [CONFIG['ANDROID_APPCOMPAT_V7_AAR_LIB']]
 gbjar.extra_jars += [CONFIG['ANDROID_SUPPORT_VECTOR_DRAWABLE_AAR_LIB']]
 gbjar.extra_jars += [CONFIG['ANDROID_ANIMATED_VECTOR_DRAWABLE_AAR_LIB']]
 gbjar.extra_jars += [CONFIG['ANDROID_CARDVIEW_V7_AAR_LIB']]
 gbjar.extra_jars += [CONFIG['ANDROID_DESIGN_AAR_LIB']]
 gbjar.extra_jars += [CONFIG['ANDROID_RECYCLERVIEW_V7_AAR_LIB']]
 gbjar.extra_jars += [CONFIG['ANDROID_CUSTOMTABS_AAR_LIB']]
 
-gbjar.javac_flags += ['-Xlint:all,-deprecation,-fallthrough', '-J-Xmx512m', '-J-Xms128m']
+gbjar.javac_flags += ['-Xlint:all,-deprecation,-fallthrough,-cast', '-J-Xmx512m', '-J-Xms128m']
 
 # gecko-thirdparty is a good place to put small independent libraries
 gtjar = add_java_jar('gecko-thirdparty')
 gtjar.sources += [ thirdparty_source_dir + f for f in [
     'com/booking/rtlviewpager/PagerAdapterWrapper.java',
     'com/booking/rtlviewpager/RtlViewPager.java',
     'com/jakewharton/disklrucache/DiskLruCache.java',
     'com/jakewharton/disklrucache/StrictLineReader.java',