[Android] Enable multidex for debug builds of ChromePublic.

base/BUILD.gn

Index: base/BUILD.gn
diff --git a/base/BUILD.gn b/base/BUILD.gn
index 3c9089d2fa6fe71805ca520ef490628a03b4303a..9e4270d26009f853e37dc7af883bed4cb43705c8 100644
--- a/base/BUILD.gn
+++ b/base/BUILD.gn
@@ -1650,6 +1650,7 @@ if (is_android) {
   android_library("base_java") {
     srcjar_deps = [
       ":base_android_java_enums_srcjar",
+      ":base_multidex_gen",
       ":base_native_libraries_gen",
     ]
 
@@ -1725,6 +1726,14 @@ if (is_android) {
     ]
   }
 
+  # GYP: //base/base.gyp:base_multidex_gen
+  java_cpp_template("base_multidex_gen") {
+    sources = [
+      "android/java/templates/ChromiumMultiDex.template",
+    ]
+    package_name = "org/chromium/base/multidex"
+  }
+
   # GYP: //base/base.gyp:base_native_libraries_gen
   java_cpp_template("base_native_libraries_gen") {
     sources = [