Add filtering by priority in the Network filter area.

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

Index: third_party/WebKit/Source/devtools/front_end/components/NetworkConditionsSelector.js
diff --git a/third_party/WebKit/Source/devtools/front_end/components/NetworkConditionsSelector.js b/third_party/WebKit/Source/devtools/front_end/components/NetworkConditionsSelector.js
index fc19d6e08fe92bae648728321f050f37230e72b3..6f96f8fee3283a00aaf376868669617f5fe7bb01 100644
--- a/third_party/WebKit/Source/devtools/front_end/components/NetworkConditionsSelector.js
+++ b/third_party/WebKit/Source/devtools/front_end/components/NetworkConditionsSelector.js
@@ -501,3 +501,21 @@ Components.uiLabelForPriority = function(priority) {
   }
   return labelMap.get(priority) || Common.UIString('Unknown');
 };
+
+/**
+ * @param {string} priorityLabel
+ * @return {string}
+ */
+Components.priorityByUiLabel = function(priorityLabel) {

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

nit: lets rename to: "uiLabelToPriority"

+  var labelToPriorityMap = Components.priorityByUiLabel._uILabelToPriority;

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

Lets restructure this function to something like:

if (Components.uiLabelForPriority._uiLabelToPriorityMap)
  return Components.uiLabelForPriority._uiLabelToPriorityMap.get(priorityLabel);

var map = Components.priorityUiLabelMap().inverse();
Components.uiLabelForPriority._uiLabelToPriorityMap = map;
return map.get(priorityLabel) || '';

+  var labelMap;
+
+  if (!labelToPriorityMap) {
+    labelMap = Components.uiLabelForPriority._priorityToUILabel;

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

This may not be set yet.

+    labelToPriorityMap = Object.keys(Protocol.Network.ResourcePriority)
+                             .reduce(((map, priority) => map.set(labelMap.get(priority), priority)), new Map());

[Oleksii Kadurin, 2016/12/13 19:43:37]

* I know that such a huge indentation here looks ugly. But it's what
clang-format have me to do.
* I move the property 'labelMap' out of the 'if' block. But I'm not sure how it
works at the end. I've noticed that usually code style differs from what I've
seen before. It's ok here to have 'var' declarations inside the condition/loop
blocks, even though there's only function scope when it comes to 'var'
declarations.
Is it because at the end all the JS code is somehow transpiled to something else
to have ability to run devtools as a part of the whole browser?
* Unfortunately I'm still not sure if what I made in case of
'labelToPriorityMap' is a proper creation of inverse map. 

+    Components.priorityByUiLabel._uILabelToPriority = labelToPriorityMap;
+  }
+
+  return labelToPriorityMap.get(priorityLabel);
+};