headless: support --disk-cache-dir flag

The --disk-cache-dir flag allows to use custom disk cache folder instead
of using the one inferred from user data directory.

BUG=882431
R=caseq

Change-Id: I2da7e1c4b72eda32bccf6851c66ce44c1aaa837d
Reviewed-on: https://chromium-review.googlesource.com/c/1359038Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Commit-Queue: Andrey Lushnikov <lushnikov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#613297}

headless/app/headless_shell_switches.cc

@@ -34,6 +34,10 @@ const char kCrashDumpsDir[] = "crash-dumps-dir";
 // (experimental).
 const char kDeterministicMode[] = "deterministic-mode";
 
+// Use a specific disk cache location, rather than one derived from the
+// UserDatadir.
+const char kDiskCacheDir[] = "disk-cache-dir";
+
 // Instructs headless_shell to print document.body.innerHTML to stdout.
 const char kDumpDom[] = "dump-dom";
 

headless/app/headless_shell_switches.h

@@ -16,6 +16,7 @@ HEADLESS_EXPORT extern const char kDefaultBackgroundColor[];
 HEADLESS_EXPORT extern const char kDeterministicMode[];
 HEADLESS_EXPORT extern const char kDisableCookieEncryption[];
 HEADLESS_EXPORT extern const char kDisableCrashReporter[];
+HEADLESS_EXPORT extern const char kDiskCacheDir[];
 HEADLESS_EXPORT extern const char kDumpDom[];
 HEADLESS_EXPORT extern const char kEnableBeginFrameControl[];
 HEADLESS_EXPORT extern const char kEnableCrashReporter[];

headless/lib/browser/headless_request_context_manager.cc

@@ -397,6 +397,12 @@ HeadlessRequestContextManager::CreateNetworkContextParams() {
         user_data_path_.Append(FILE_PATH_LITERAL("Cookies"));
     context_params->channel_id_path =
         user_data_path_.Append(FILE_PATH_LITERAL("Origin Bound Certs"));
+  }
+  base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
+  if (command_line->HasSwitch(switches::kDiskCacheDir)) {
+    context_params->http_cache_path =
+        command_line->GetSwitchValuePath(switches::kDiskCacheDir);
+  } else if (!user_data_path_.empty()) {
     context_params->http_cache_path =
         user_data_path_.Append(FILE_PATH_LITERAL("Cache"));
   }