core(network): handle LR transferSize

lighthouse-core/lib/network-request.js

@@ -93,6 +93,8 @@ module.exports = class NetworkRequest {
     this.initiatorRequest = undefined;
     /** @type {HeaderEntry[]} */
     this.responseHeaders = [];
+    /** @type {string} */
+    this.responseHeadersText = '';
 
     this.fetchedViaServiceWorker = false;
     /** @type {string|undefined} */
@@ -172,6 +174,7 @@ module.exports = class NetworkRequest {
     }
 
     this._updateResponseReceivedTimeIfNecessary();
+    this._updateTransferSizeForLightRiderIfNecessary();
   }
 
   /**
@@ -234,12 +237,15 @@ module.exports = class NetworkRequest {
     this.timing = response.timing;
     if (resourceType) this.resourceType = RESOURCE_TYPES[resourceType];
     this.mimeType = response.mimeType;
+    this.responseHeadersText = response.headersText || '';
     this.responseHeaders = NetworkRequest._headersDictToHeadersArray(response.headers);
 
     this.fetchedViaServiceWorker = !!response.fromServiceWorker;
 
     if (this.fromMemoryCache) this.timing = undefined;
     if (this.timing) this._recomputeTimesWithResourceTiming(this.timing);
+
+    this._updateTransferSizeForLightRiderIfNecessary();
   }
 
   /**
@@ -269,6 +275,28 @@ module.exports = class NetworkRequest {
     this.responseReceivedTime = Math.min(this.endTime, this.responseReceivedTime);
   }
 
+  /**
+   * LR loses transfer size information and passes it in the 'X-Original-Content-Length' header.
+   */
+  _updateTransferSizeForLightRiderIfNecessary() {
+    // Bail if we're not in LightRider, this only applies there.
+    if (!global.isLightRider) return;
+    // Bail if we somehow already have transfer size data.
+    if (this.transferSize) return;
+    // Bail if we didn't get any response headers.
+    if (!this.responseHeadersText) return;
+
+    const originalContentLength = this.responseHeaders.
+      find(item => item.name === 'X-Original-Content-Length');
+    // Bail if the x-original-content-length header was missing.
+    if (!originalContentLength) return;
+
+    // Transfer size is the original content length + length of headers
+    const contentBytes = parseFloat(originalContentLength.value);
+    const headerBytes = this.responseHeadersText.length;
+    this.transferSize = contentBytes + headerBytes;
+  }
+
   /**
    * Convert the requestId to backend-version by removing the `:redirect` portion
    *

lighthouse-extension/app/src/lighthouse-ext-background.js

@@ -95,6 +95,9 @@ async function runLighthouseInExtension(flags, categoryIDs) {
  * @return {Promise<string|Array<string>|void>}
  */
 async function runLighthouseInLR(connection, url, flags, {lrDevice, categoryIDs, logAssets}) {
+  // Certain fixes need to kick-in under LR, see https://github.com/GoogleChrome/lighthouse/issues/5839
+  global.isLightRider = true;
+
   // Override default device to be desktop, since LR default device has viewport 1x1.
   connection.sendCommand('Emulation.setDeviceMetricsOverride',
     {width: 800, height: 600, deviceScaleFactor: 0, mobile: false});

typings/node.d.ts

@@ -0,0 +1,11 @@
+/**
+ * @license Copyright 2018 Google Inc. All Rights Reserved.
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.
+ */
+
+declare module NodeJS {
+  interface Global {
+    isLightRider?: boolean;
+  }
+}