Add filtering by priority in the Network filter area.

third_party/WebKit/Source/devtools/front_end/components/NetworkConditionsSelector.js

 // Copyright 2015 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.
 /**
  * @unrestricted
  */
 Components.NetworkConditionsSelector = class {
   /**
    * @param {function(!Array<!Components.NetworkConditionsGroup>):!Array<?SDK.NetworkManager.Conditions>} populateCallback
    * @param {function(number)} selectCallback
@@ skipping 483 matching lines @@
       [Protocol.Network.ResourcePriority.VeryLow, Common.UIString('Lowest')],
       [Protocol.Network.ResourcePriority.Low, Common.UIString('Low')],
       [Protocol.Network.ResourcePriority.Medium, Common.UIString('Medium')],
       [Protocol.Network.ResourcePriority.High, Common.UIString('High')],
       [Protocol.Network.ResourcePriority.VeryHigh, Common.UIString('Highest')]
     ]);
     Components.uiLabelForPriority._priorityToUILabel = labelMap;
   }
   return labelMap.get(priority) || Common.UIString('Unknown');
 };
+
+/**
+ * @param {string} priorityLabel
+ * @return {string|undefined}
+ */
+Components.getPriorityByPriorityLabel = function(priorityLabel) {

[allada, 2016/12/12 17:29:57]

Instead of doing this lets generate an inverse map.

example:
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/devtools/front...

[Oleksii Kadurin, 2016/12/12 21:13:15]

1. 'inverse map' - do you mean every time the function
getPriorityByPriorityLabel is called it should generate inverse map and use the
function's key argument as a key of inverse map to return a value? 
2. In the example you provided they generate array of values by key/value
object. Sorry, but I don't really understand how it might help me. Could you
please be more specific here?

[allada, 2016/12/12 23:51:08]

We already generate a map one time for ENUM => symbol, but I'm suggesting at the
same time we generate another UIStringKey => symbol map. This way it'll allow us
just lookup what symbol to use from a UIStringKey.

+  var labelMap = Components.uiLabelForPriority._priorityToUILabel;
+  var result;
+
+  labelMap.forEach(function(value, key) {
+    if (value === priorityLabel)
+      result = key;
+  });
+
+  return result;
+};