Bug 1206048 - Remove E10S_WINDOW metric. r=Dexter

Removed the histogram |E10S_WINDOW| and related code as it is no longer in use.

browser/base/content/browser.js

@@ -1268,8 +1268,6 @@ var gBrowserInit = {
     PanelUI.init();
     LightweightThemeListener.init();
 
-    Services.telemetry.getHistogramById("E10S_WINDOW").add(gMultiProcessBrowser);
-
     SidebarUI.startDelayedLoad();
 
     UpdateUrlbarSearchSplitterState();

toolkit/components/telemetry/Histograms.json

@@ -8890,11 +8890,6 @@
     "bug_numbers": [1241294],
     "description": "Why e10s is enabled or disabled (0=ENABLED_BY_USER, 1=ENABLED_BY_DEFAULT, 2=DISABLED_BY_USER, 3=DISABLED_IN_SAFE_MODE, 4=DISABLED_FOR_ACCESSIBILITY, 5=DISABLED_FOR_MAC_GFX, 6=DISABLED_FOR_BIDI, 7=DISABLED_FOR_ADDONS, 8=FORCE_DISABLED, 9=DISABLED_FOR_XPLAYERS, 10=DISABLED_FOR_OS_VERSION)"
   },
-  "E10S_WINDOW": {
-    "expires_in_version": "never",
-    "kind": "boolean",
-    "description": "Whether a browser window is set as an e10s window"
-  },
   "E10S_BLOCKED_FROM_RUNNING": {
     "expires_in_version": "never",
     "kind": "boolean",

toolkit/components/telemetry/histogram-whitelists.json

@@ -221,7 +221,6 @@
     "DWRITEFONT_DELAYEDINITFONTLIST_TOTAL",
     "DWRITEFONT_INIT_PROBLEM",
     "E10S_BLOCKED_FROM_RUNNING",
-    "E10S_WINDOW",
     "ENABLE_PRIVILEGE_EVER_CALLED",
     "FENNEC_DISTRIBUTION_CODE_CATEGORY",
     "FENNEC_DISTRIBUTION_DOWNLOAD_TIME_MS",
@@ -959,7 +958,6 @@
     "DWRITEFONT_DELAYEDINITFONTLIST_TOTAL",
     "DWRITEFONT_INIT_PROBLEM",
     "E10S_BLOCKED_FROM_RUNNING",
-    "E10S_WINDOW",
     "ENABLE_PRIVILEGE_EVER_CALLED",
     "FENNEC_DISTRIBUTION_CODE_CATEGORY",
     "FENNEC_DISTRIBUTION_DOWNLOAD_TIME_MS",