Revert of Revert of DevTools: allow storing devtools preferences on the browser side. [blink]

Source/devtools/front_end/main/Main.js

Index: Source/devtools/front_end/main/Main.js
diff --git a/Source/devtools/front_end/main/Main.js b/Source/devtools/front_end/main/Main.js
index 15a90efe4d70583ce9f6ec2b0d70362009bdcb78..c388bba8ce1e1eff38b7103dbcb1f0bff75f713f 100644
--- a/Source/devtools/front_end/main/Main.js
+++ b/Source/devtools/front_end/main/Main.js
@@ -117,21 +117,63 @@
 
         if (InspectorFrontendHost.isUnderTest())
             self.runtime.useTestBase();
-        this._createSettings();
+        InspectorFrontendHost.getPreferences(this._createSettings.bind(this));
+    },
+
+    /**
+     * @param {!Object<string, string>} prefs
+     */
+    _createSettings: function(prefs)
+    {
+        // Patch settings from the URL param (for tests).
+        var settingsParam = Runtime.queryParam("settings");
+        if (settingsParam) {
+            try {
+                var settings = JSON.parse(window.decodeURI(settingsParam));
+                for (var key in settings)
+                    prefs[key] = settings[key];
+            } catch(e) {
+                // Ignore malformed settings.
+            }
+        }
+
+        this._initializeExperiments(prefs);
+
+        /**
+         * @param {!Array<{name: string}>} changes
+         */
+        function trackPrefsObject(changes)
+        {
+            if (!Object.keys(prefs).length) {
+                InspectorFrontendHost.clearPreferences();
+                return;
+            }
+
+            for (var change of changes) {
+                var name = change.name;
+                if (name in prefs)
+                    InspectorFrontendHost.setPreference(name, prefs[name]);
+                else
+                    InspectorFrontendHost.removePreference(name);
+            }
+        }
+
+        Object.observe(prefs, trackPrefsObject);
+        WebInspector.settings = new WebInspector.Settings(prefs);
+
+        if (!InspectorFrontendHost.isUnderTest()) {
+            // This setting is needed for backwards compatibility with Devtools CodeSchool extension. DO NOT REMOVE
+            WebInspector.settings.pauseOnExceptionStateString = new WebInspector.PauseOnExceptionStateSetting();
+            new WebInspector.VersionController().updateVersion();
+        }
+
         this._createAppUI();
     },
 
-    _createSettings: function()
-    {
-        this._initializeExperiments();
-        WebInspector.settings = new WebInspector.Settings();
-
-        // This setting is needed for backwards compatibility with Devtools CodeSchool extension. DO NOT REMOVE
-        WebInspector.settings.pauseOnExceptionStateString = new WebInspector.PauseOnExceptionStateSetting();
-        new WebInspector.VersionController().updateVersion();
-    },
-
-    _initializeExperiments: function()
+    /**
+     * @param {!Object<string, string>} prefs
+     */
+    _initializeExperiments: function(prefs)
     {
         Runtime.experiments.register("accessibilityInspection", "Accessibility Inspection", true);
         Runtime.experiments.register("animationInspection", "Animation Inspection");
@@ -161,8 +203,8 @@
         Runtime.experiments.cleanUpStaleExperiments();
 
         if (InspectorFrontendHost.isUnderTest()) {
+            var testPath = JSON.parse(prefs["testPath"] || "\"\"");
             // Enable experiments for testing.
-            var testPath = self.localStorage ? self.localStorage["testPath"] || "" : "";
             if (testPath.indexOf("debugger/promise") !== -1)
                 Runtime.experiments.enableForTest("promiseTracker");
             if (testPath.indexOf("elements/") !== -1)