Serve mojo WebUI resources from the same origin as the WebUI itself.

content/browser/webui/web_ui_mojo_browsertest.cc

Index: content/browser/webui/web_ui_mojo_browsertest.cc
diff --git a/content/browser/webui/web_ui_mojo_browsertest.cc b/content/browser/webui/web_ui_mojo_browsertest.cc
index 3f5a6de8118d98975cc4ac1c2c3ececee13bf1e2..9d941c9f6c1a7f33d46a864ae43386538eb2df82 100644
--- a/content/browser/webui/web_ui_mojo_browsertest.cc
+++ b/content/browser/webui/web_ui_mojo_browsertest.cc
@@ -7,6 +7,7 @@
 #include "base/command_line.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
+#include "base/path_service.h"
 #include "base/run_loop.h"
 #include "base/strings/string_util.h"
 #include "content/browser/webui/web_ui_controller_factory_registry.h"
@@ -52,10 +53,22 @@ bool GetResource(const std::string& id,
       id == mojo::kValidatorModuleName)
     return false;
 
+  if (id.find(".mojom") != std::string::npos) {
+    std::string contents;
+    CHECK(base::ReadFileToString(mojo::test::GetFilePathForJSResource(id),
+                                 &contents, std::string::npos))
+        << id;
+    base::RefCountedString* ref_contents = new base::RefCountedString;
+    ref_contents->data() = contents;
+    callback.Run(ref_contents);
+    return true;
+  }
+
+  base::FilePath path;
+  DCHECK(base::PathService::Get(content::DIR_TEST_DATA, &path));
+  path = path.AppendASCII(id.substr(0, id.find("?")));
   std::string contents;
-  CHECK(base::ReadFileToString(mojo::test::GetFilePathForJSResource(id),
-                               &contents,
-                               std::string::npos)) << id;
+  CHECK(base::ReadFileToString(path, &contents, std::string::npos)) << id;

[magjed_chromium, 2015/11/24 08:55:50]

After your CL, we are hitting this CHECK on the Cast Linux bot,
content_browsertests, with the following failing tests:
WebUIMojoTest.EndToEndPing and WebUIMojoTest.ConnectToApplication.
https://build.chromium.org/p/chromium.linux/builders/Cast%20Linux/builds/1315...

   base::RefCountedString* ref_contents = new base::RefCountedString;
   ref_contents->data() = contents;
   callback.Run(ref_contents);
@@ -90,13 +103,14 @@ class BrowserTargetImpl : public BrowserTarget {
 // WebUIController that sets up mojo bindings.
 class TestWebUIController : public WebUIController {
  public:
-   TestWebUIController(WebUI* web_ui, base::RunLoop* run_loop)
-      : WebUIController(web_ui),
-        run_loop_(run_loop) {
+  TestWebUIController(WebUI* web_ui, base::RunLoop* run_loop)
+      : WebUIController(web_ui), run_loop_(run_loop) {
     content::WebUIDataSource* data_source =
-        WebUIDataSource::AddMojoDataSource(
-            web_ui->GetWebContents()->GetBrowserContext());
+        WebUIDataSource::Create("mojo-web-ui");
+    data_source->AddMojoResources();
     data_source->SetRequestFilter(base::Bind(&GetResource));
+    content::WebUIDataSource::Add(web_ui->GetWebContents()->GetBrowserContext(),
+                                  data_source);
   }
 
  protected:
@@ -205,7 +219,7 @@ IN_PROC_BROWSER_TEST_F(WebUIMojoTest, EndToEndPing) {
   ASSERT_TRUE(embedded_test_server()->Start());
   base::RunLoop run_loop;
   factory()->set_run_loop(&run_loop);
-  GURL test_url(embedded_test_server()->GetURL("/web_ui_mojo.html?ping"));
+  GURL test_url("chrome://mojo-web-ui/web_ui_mojo.html?ping");
   NavigateToURL(shell(), test_url);
   // RunLoop is quit when message received from page.
   run_loop.Run();
@@ -234,7 +248,7 @@ IN_PROC_BROWSER_TEST_F(WebUIMojoTest, ConnectToApplication) {
 
   ASSERT_TRUE(embedded_test_server()->Start());
   NavigateToURL(shell(),
-                embedded_test_server()->GetURL("/web_ui_mojo_shell_test.html"));
+                GURL("chrome://mojo-web-ui/web_ui_mojo_shell_test.html"));
 
   DOMMessageQueue message_queue;
   std::string message;