[Android] Add gyp support for multidex.

base/base.gyp

Index: base/base.gyp
diff --git a/base/base.gyp b/base/base.gyp
index 65f6d7d89d9acc58ff387d195760460653174391..97c61d271b20ed6cef02f81447c4589a5d757e0a 100644
--- a/base/base.gyp
+++ b/base/base.gyp
@@ -1450,6 +1450,7 @@
             'base_java_library_process_type',
             'base_java_memory_pressure_level',
             'base_native_libraries_gen',
+            '../third_party/android_tools/android_tools.gyp:android_support_multidex_javalib',
             '../third_party/jsr-305/jsr-305.gyp:jsr_305_javalib',
           ],
           'includes': [ '../build/java.gypi' ],
@@ -1507,12 +1508,30 @@
           'includes': [ '../build/java.gypi' ],
         },
         {
+          # TODO(jbudorick): Remove this once we roll to robolectric 3.0 and pull
+          # in the multidex shadow library. crbug.com/522043
+          # GN: //base:base_junit_test_support
+          'target_name': 'base_junit_test_support',
+          'type': 'none',
+          'dependencies': [
+            '../testing/android/junit/junit_test.gyp:junit_test_support',
+            '../third_party/android_tools/android_tools.gyp:android_support_multidex_javalib',
+          ],
+          'variables': {
+            'src_paths': [
+              '../base/test/android/junit/',
+            ],
+          },
+          'includes': [ '../build/host_jar.gypi' ]
+        },
+        {
           # GN: //base:base_junit_tests
           'target_name': 'base_junit_tests',
           'type': 'none',
           'dependencies': [
             'base_java',
             'base_java_test_support',
+            'base_junit_test_support',
             '../testing/android/junit/junit_test.gyp:junit_test_support',
           ],
           'variables': {