Add Keep annotations to abstract components

platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/http/NativeHttpRequest.java

@@ -5,6 +5,7 @@
 
 import java.util.concurrent.locks.ReentrantLock;
 
+@Keep
 public class NativeHttpRequest implements HttpResponder {
 
   private final HttpRequest httpRequest = Mapbox.getModuleProvider().createHttpRequest();

platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/log/Logger.java

@@ -1,5 +1,6 @@
 package com.mapbox.mapboxsdk.log;
 
+import android.support.annotation.Keep;
 import android.util.Log;
 
 /**
@@ -9,6 +10,7 @@
  * Alternative implementations can be set with {@link #setLoggerDefinition(LoggerDefinition)}.
  * </p>
  */
+@Keep
 public final class Logger {
 
   private static final LoggerDefinition DEFAULT = new LoggerDefinition() {

platform/android/MapboxGLAndroidSDKTestApp/build.gradle

@@ -34,12 +34,14 @@ android {
 
     buildTypes {
         debug {
-            testCoverageEnabled = true
+            testCoverageEnabled true
             minifyEnabled false
+            shrinkResources false
             proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
         }
         release {
             minifyEnabled true
+            shrinkResources true
             proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
             signingConfig signingConfigs.debug
         }