Add filtering by priority in the Network filter area.

third_party/WebKit/Source/devtools/front_end/network/NetworkDataGridNode.js

Index: third_party/WebKit/Source/devtools/front_end/network/NetworkDataGridNode.js
diff --git a/third_party/WebKit/Source/devtools/front_end/network/NetworkDataGridNode.js b/third_party/WebKit/Source/devtools/front_end/network/NetworkDataGridNode.js
index e62d3fb47c9a37582dc2be94b2989415f41c7d3a..ae7867fcee3e85d9d809be9d7e1987320ee11b23 100644
--- a/third_party/WebKit/Source/devtools/front_end/network/NetworkDataGridNode.js
+++ b/third_party/WebKit/Source/devtools/front_end/network/NetworkDataGridNode.js
@@ -168,10 +168,10 @@ Network.NetworkDataGridNode = class extends UI.SortableDataGridNode {
    * @return {number}
    */
   static InitialPriorityComparator(a, b) {
-    var priorityMap = Network.NetworkDataGridNode._symbolicToNumericPriority;
+    var priorityMap = Network.NetworkDataGridNode.symbolicToNumericPriority;
     if (!priorityMap) {
-      Network.NetworkDataGridNode._symbolicToNumericPriority = new Map();
-      priorityMap = Network.NetworkDataGridNode._symbolicToNumericPriority;
+      Network.NetworkDataGridNode.symbolicToNumericPriority = new Map();

[allada, 2016/12/17 01:20:20]

Lets extract part of this into something like: "symbolicToNumericMap()"
function.

I know you already did this once and put it back, but lets put it in
NetworkConditionsSelector.

Can you please also put a todo above the function reading:

// TODO(allada) This function deserves to be in a network-common of some sort.

+      priorityMap = Network.NetworkDataGridNode.symbolicToNumericPriority;
       priorityMap.set(Protocol.Network.ResourcePriority.VeryLow, 1);
       priorityMap.set(Protocol.Network.ResourcePriority.Low, 2);
       priorityMap.set(Protocol.Network.ResourcePriority.Medium, 3);