android: Hide JNI exports by default.

build/android/android_exports.gyp

Index: build/android/android_exports.gyp
diff --git a/build/android/android_exports.gyp b/build/android/android_exports.gyp
index c259eee3756c495e7198e1a2c922d2a4b2f1a6dd..bf3424d73fb13d5e8706e092b4f72666e40973f9 100644
--- a/build/android/android_exports.gyp
+++ b/build/android/android_exports.gyp
@@ -2,13 +2,20 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+# This target is only used when android_webview_build==1 - it implements a
+# whitelist for exported symbols to minimise the binary size and prevent us
+# accidentally exposing things we don't mean to expose.
+
 {
+  'variables': {
+    'android_linker_script%': '<(SHARED_INTERMEDIATE_DIR)/android_webview_export_whitelist.lst',
+  },
   'targets': [
     {
       'target_name': 'android_exports',
       'type': 'none',
       'inputs': [
-        '<(DEPTH)/build/android/android_exports.lst',
+        '<(DEPTH)/build/android/android_webview_export_whitelist.lst',
       ],
       'outputs': [
         '<(android_linker_script)',
@@ -28,9 +35,6 @@
               # Only export symbols that are specified in version script.
               '-Wl,--version-script=<(android_linker_script)',
             ],
-            'ldflags!': [
-              '-Wl,--exclude-libs=ALL',
-            ],
           },
         }],
       ],