Implement a basic PPAPI plugin for Blink layout tests.

content/content_shell.gypi

Index: content/content_shell.gypi
diff --git a/content/content_shell.gypi b/content/content_shell.gypi
index 20a33d9697c6786a05e22ce0ed48e0602472926c..a74cd65c4096fe92619c6dffa460d357600b94cf 100644
--- a/content/content_shell.gypi
+++ b/content/content_shell.gypi
@@ -62,6 +62,7 @@
         '../media/media.gyp:media',
         '../net/net.gyp:net',
         '../net/net.gyp:net_resources',
+        '../ppapi/ppapi_internal.gyp:blink_test_plugin',
         '../skia/skia.gyp:skia',
         '../storage/storage_browser.gyp:storage',
         '../third_party/WebKit/public/blink.gyp:blink',
@@ -735,6 +736,12 @@
           ],
           'copies': [
             {
+              'destination': '<(PRODUCT_DIR)/$(CONTENTS_FOLDER_PATH)',

[dcheng, 2015/12/01 01:03:30]

This is slightly horrible, but it seems to be the easiest way to integrate with
the assumption that PPAPI test plugins live in DIR_MODULE.

Otherwise, a Mac static_library content_shell build fails to find the test
plugin.

+              'files': [
+                '<(PRODUCT_DIR)/blink_test_plugin.plugin',
+              ],
+            },
+            {
               'destination': '<(PRODUCT_DIR)/$(CONTENTS_FOLDER_PATH)/Resources',
               'files': [
                 '<(PRODUCT_DIR)/crash_inspector',