Implementing TabManager extensions API Discard Function.

chrome/common/extensions/api/tabs.json

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 [
   {
     "namespace": "tabs",
     "description": "Use the <code>chrome.tabs</code> API to interact with the browser's tab system. You can use this API to create, modify, and rearrange tabs in the browser.",
     "types": [
       { "id": "MutedInfoReason",
@@ skipping 889 matching lines @@
             "description": "Called with the tab's current zoom settings.",
             "parameters": [
               {
                 "$ref": "ZoomSettings",
                 "name": "zoomSettings",
                 "description": "The tab's current zoom settings."
               }
             ]
           }
         ]
+      },
+      {
+        "name": "discard",
+        "type": "function",
+        "description": "Discards a tab from memory. Discarded tabs are still visible on the tab strip and get reloaded when activated.",

[Devlin, 2016/07/21 15:39:21]

nit: s/get reloaded/are reloaded

I also wonder if the "reloaded" terminology here is a little ambiguous, because
we page the tab back into memory rather than refreshing the page.  Is there
another canonical way of saying this?  If not, this probably isn't that bad.

[Anderson Silva, 2016/07/21 20:43:04]

Reloaded is what we've always been using, so we are using here for consistency. 

[Georges Khalil, 2016/07/21 21:02:23]

We can definitely revisit the "reload" terminology and find a better word for
it, but consistency for now is good.

Just a quick comment that the tab does somewhat get refreshed, albeit mostly
from cache when possible. But sites such as GMail get reloaded from network
entirely.

If you have suggestions, we're all ears! :)

+        "parameters": [
+          {
+            "type": "integer",
+            "name": "tabId",
+            "optional": true,
+            "minimum": 0,
+            "description": "The ID of the tab to be discarded; defaults to the least important tab."
+          },
+          {
+            "type": "function",
+            "name": "callback",
+            "optional": true,
+            "description": "Called after the operation is completed.",
+            "parameters": [
+              {
+                "name": "tab",
+                "$ref": "Tab",
+                "description": "Discarded tab if it was successfully discarded."

[Devlin, 2016/07/21 15:39:21]

Tying into the comment in the api.cc file, could this be an optional param,
which would indicate success by its presence?

[Anderson Silva, 2016/07/21 20:43:04]

Solved by removing the boolean and by returning undefined in case of failure.

+              },
+              {
+                "name": "success",
+                "type": "boolean",
+                "description": "Status describing if the tab was successfully discarded or not."
+              }
+            ]
+          }
+        ]
       }
     ],
     "events": [
       {
         "name": "onCreated",
         "type": "function",
         "description": "Fired when a tab is created. Note that the tab's URL may not be set at the time this event fired, but you can listen to onUpdated events to be notified when a URL is set.",
         "parameters": [
           {
             "$ref": "Tab",
@@ skipping 264 matching lines @@
             "tabId": {"type": "integer", "minimum": 0},
             "oldZoomFactor": {"type": "number"},
             "newZoomFactor": {"type": "number"},
             "zoomSettings": {"$ref": "ZoomSettings"}
           }
         }]
       }
     ]
   }
 ]