[NaCl SDK] Add pepper_38 to naclsdk_manifest2.json

R=binji@chromium.org

Review URL: https://codereview.chromium.org/514333002

Cr-Commit-Position: refs/heads/master@{#292478}

native_client_sdk/src/build_tools/json/naclsdk_manifest2.json

@@ -202,6 +202,16 @@
       "stability": "post_stable",
       "version": 37
     },
+    {
+      "archives": [],
+      "description": "Chrome 38 bundle, revision xxxxx",
+      "name": "pepper_38",
+      "recommended": "no",
+      "repath": "pepper_38",
+      "revision": 0,
+      "stability": "post_stable",
+      "version": 38
+    },
     {
       "archives": [],
       "description": "Chrome Canary",