Report unprocessed network request count in troubleshooting info

Related discussion:
- https://github.com/uBlockOrigin/uAssets/discussions/16939

platform/common/vapi-background.js

@@ -1175,6 +1175,7 @@ vAPI.Net = class {
         this.suspendableListener = undefined;
         this.listenerMap = new WeakMap();
         this.suspendDepth = 0;
+        this.unprocessedRequestCount = 0;
 
         browser.webRequest.onBeforeRequest.addListener(
             details => {
@@ -1227,8 +1228,10 @@ vAPI.Net = class {
         );
     }
     onBeforeSuspendableRequest(details) {
-        if ( this.suspendableListener === undefined ) { return; }
-        return this.suspendableListener(details);
+        if ( this.suspendableListener !== undefined ) {
+            return this.suspendableListener(details);
+        }
+        this.unprocessedRequestCount += 1;
     }
     setSuspendableListener(listener) {
         this.suspendableListener = listener;

src/js/assets.js

@@ -560,7 +560,7 @@ const assetCacheRead = async function(assetKey, updateReadTime = false) {
 
     µb.supportStats.maxAssetCacheWait = Math.max(
         Date.now() - t0,
-        parseInt(µb.supportStats.maxAssetCacheWait, 10)
+        parseInt(µb.supportStats.maxAssetCacheWait, 10) || 0
     ) + ' ms';
 
     if (

src/js/background.js

@@ -219,8 +219,9 @@ const µBlock = {  // jshint ignore:line
     readyToFilter: false,
 
     supportStats: {
-        allReadyAfter: '',
-        maxAssetCacheWait: '0 ms',
+        allReadyAfter: '?',
+        maxAssetCacheWait: '?',
+        unprocessedRequestCount: '?',
     },
 
     pageStores: new Map(),

src/js/traffic.js

@@ -1147,6 +1147,7 @@ const webRequest = {
                 }
             );
             vAPI.net.unsuspend({ all: true });
+            µb.supportStats.unprocessedRequestCount = `${vAPI.net.unprocessedRequestCount}`;
         };
     })(),