DevTools: do not fall back to image request re-issue for no-cache requests.

Bug: 816688
Change-Id: I29beeae9ce49169204ec867cc9636b00a360a26a
Reviewed-on: https://chromium-review.googlesource.com/941980Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Pavel Feldman <pfeldman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#540722}

third_party/WebKit/Source/devtools/front_end/sdk/NetworkRequest.js

@@ -1032,11 +1032,11 @@ SDK.NetworkRequest = class extends Common.Object {
      */
     function onResourceContent(content) {
       let imageSrc = Common.ContentProvider.contentAsDataURL(content, this._mimeType, true);
-      if (imageSrc === null)
+      const cacheControl = this.responseHeaderValue('cache-control');
+      if (imageSrc === null && (!cacheControl || !cacheControl.includes('no-cache')))
         imageSrc = this._url;
       image.src = imageSrc;
     }
-
     this.requestContent().then(onResourceContent.bind(this));
   }