Add support for calling the java Callback from native.

base/BUILD.gn

Index: base/BUILD.gn
diff --git a/base/BUILD.gn b/base/BUILD.gn
index fcd6803a6e0af6c061e3cbfed58c01b35ac8b9c0..5712663ed8bc334414a91a68cdc0ea64eb9ce422 100644
--- a/base/BUILD.gn
+++ b/base/BUILD.gn
@@ -148,6 +148,8 @@ component("base") {
     "android/base_jni_registrar.h",
     "android/build_info.cc",
     "android/build_info.h",
+    "android/callback_android.cc",
+    "android/callback_android.h",
     "android/command_line_android.cc",
     "android/command_line_android.h",
     "android/content_uri_utils.cc",
@@ -2132,6 +2134,7 @@ if (is_android) {
       "android/java/src/org/chromium/base/ApkAssets.java",
       "android/java/src/org/chromium/base/ApplicationStatus.java",
       "android/java/src/org/chromium/base/BuildInfo.java",
+      "android/java/src/org/chromium/base/Callback.java",
       "android/java/src/org/chromium/base/CommandLine.java",
       "android/java/src/org/chromium/base/ContentUriUtils.java",
       "android/java/src/org/chromium/base/ContextUtils.java",