Up until a week or so ago I was able to find code in //src/third_party/custom_tabs_client/src through code search. This no longer works.

eg Searching for CustomTabsIntent:
https://cs.chromium.org/search/?q=CustomTabsIntent&m=100&type=cs
No longer turns up CustomTabsIntent.java, which lives at:
//src/third_party/custom_tabs_client/src/customtabs/src/android/support/customtabs/CustomTabsIntent.java

It looks like //src/third_party/custom_tabs_client/src is no longer visible in code search: https://cs.chromium.org/chromium/src/third_party/custom_tabs_client/