Introduce --remote-debugging-frontend switch for custom remote debugging front-end

chrome/browser/ui/webui/devtools_ui.cc

Index: chrome/browser/ui/webui/devtools_ui.cc
diff --git a/chrome/browser/ui/webui/devtools_ui.cc b/chrome/browser/ui/webui/devtools_ui.cc
index 1c5f89a5fc2be8a0facf5e4426a2bc00776e6185..34bfa5d9f16aaa615541a7f77a63e11db797dc01 100644
--- a/chrome/browser/ui/webui/devtools_ui.cc
+++ b/chrome/browser/ui/webui/devtools_ui.cc
@@ -4,11 +4,13 @@
 
 #include "chrome/browser/ui/webui/devtools_ui.h"
 
+#include "base/command_line.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted_memory.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "chrome/browser/profiles/profile.h"
+#include "chrome/common/chrome_switches.h"
 #include "chrome/common/url_constants.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/devtools_frontend_host.h"
@@ -16,6 +18,8 @@
 #include "content/public/browser/web_contents.h"
 #include "content/public/browser/web_ui.h"
 #include "content/public/common/user_agent.h"
+#include "net/base/filename_util.h"
+#include "net/base/load_flags.h"
 #include "net/url_request/url_fetcher.h"
 #include "net/url_request/url_fetcher_delegate.h"
 #include "net/url_request/url_request_context_getter.h"
@@ -115,6 +119,13 @@ class DevToolsDataSource : public content::URLDataSource,
                               int render_frame_id,
                               const GotDataCallback& callback);
 
+  // Serves remote DevTools frontend from any endpoint, passed through
+  // command-line flag.
+  void StartCustomDataRequest(const GURL& url,
+                              int render_process_id,
+                              int render_frame_id,
+                              const GotDataCallback& callback);
+
   ~DevToolsDataSource() override;
 
   scoped_refptr<net::URLRequestContextGetter> request_context_;
@@ -167,6 +178,40 @@ void DevToolsDataSource::StartDataRequest(
     return;
   }
 
+  base::FilePath remote_frontend_path =
+      base::CommandLine::ForCurrentProcess()->GetSwitchValuePath(
+          switches::kRemoteDebuggingFrontend);
+
+  if (remote_frontend_path.empty()) {
+    callback.Run(NULL);
+    return;
+  }
+
+  // Serve request from custom location.
+  std::string custom_path_prefix(chrome::kChromeUIDevToolsCustomPath);
+  custom_path_prefix += "/";
+
+  // Generated files should be fetched from bundle.
+  if (base::StartsWith(path, custom_path_prefix + "gen/",
+                       base::CompareCase::INSENSITIVE_ASCII)) {
+    StartBundledDataRequest(path.substr(custom_path_prefix.length()),
+                            render_process_id, render_frame_id, callback);
+    return;
+  }
+  if (base::StartsWith(path, custom_path_prefix,
+                       base::CompareCase::INSENSITIVE_ASCII)) {
+    // Create a dummy url to extract path.
+    GURL dummy_url =
+        GURL("http://example.com/" + path.substr(custom_path_prefix.length()));
+    std::string dummy_url_path = dummy_url.path();
+    base::FilePath file_path(base::FilePath::StringType(dummy_url_path.begin(),
+                                                        dummy_url_path.end()));
+    file_path = remote_frontend_path.Append(file_path);
+    GURL url = net::FilePathToFileURL(file_path);
+    StartCustomDataRequest(url, render_process_id, render_frame_id, callback);
+    return;
+  }
+
   callback.Run(NULL);
 }
 
@@ -223,6 +268,24 @@ void DevToolsDataSource::StartRemoteDataRequest(
   fetcher->Start();
 }
 
+void DevToolsDataSource::StartCustomDataRequest(
+    const GURL& url,
+    int render_process_id,
+    int render_frame_id,
+    const content::URLDataSource::GotDataCallback& callback) {
+  if (!url.is_valid()) {
+    callback.Run(
+        new base::RefCountedStaticMemory(kHttpNotFound, strlen(kHttpNotFound)));
+    return;
+  }
+  net::URLFetcher* fetcher =
+      net::URLFetcher::Create(url, net::URLFetcher::GET, this).release();
+  pending_[fetcher] = callback;
+  fetcher->SetRequestContext(request_context_.get());
+  fetcher->SetLoadFlags(net::LOAD_DISABLE_CACHE);
+  fetcher->Start();
+}
+
 void DevToolsDataSource::OnURLFetchComplete(const net::URLFetcher* source) {
   DCHECK(source);
   PendingRequestsMap::iterator it = pending_.find(source);