BlobUrlBrowserTest: Add a test exercising blob: URLs from file:// documents.

content/public/test/browser_test_base.cc

Index: content/public/test/browser_test_base.cc
diff --git a/content/public/test/browser_test_base.cc b/content/public/test/browser_test_base.cc
index 0b510beb8b483eefcdec4d63d0ceac8e1fa3d53e..493ffb04757cc44b317e16b3680d5bb6f3221eff 100644
--- a/content/public/test/browser_test_base.cc
+++ b/content/public/test/browser_test_base.cc
@@ -146,6 +146,7 @@ BrowserTestBase::BrowserTestBase()
     : expected_exit_code_(0),
       enable_pixel_output_(false),
       use_software_compositing_(false),
+      allow_file_access_from_files_(true),
       set_up_called_(false) {
 #if defined(OS_MACOSX)
   base::mac::SetOverrideAmIBundled(true);
@@ -195,8 +196,11 @@ void BrowserTestBase::SetUp() {
       switches::kIPCConnectionTimeout,
       base::Int64ToString(TestTimeouts::action_max_timeout().InSeconds()));
 
-  // The tests assume that file:// URIs can freely access other file:// URIs.
-  command_line->AppendSwitch(switches::kAllowFileAccessFromFiles);
+  // Many tests load their pages via file://, so we enable it by default, unless
+  // the test called RevokeFileAccessFromFiles() to return to the normal
+  // behavior.
+  if (allow_file_access_from_files_)
+    command_line->AppendSwitch(switches::kAllowFileAccessFromFiles);
 
   command_line->AppendSwitch(switches::kDomAutomationController);
 
@@ -388,6 +392,10 @@ void BrowserTestBase::UseSoftwareCompositing() {
   use_software_compositing_ = true;
 }
 
+void BrowserTestBase::RevokeFileAccessFromFiles() {
+  allow_file_access_from_files_ = false;
+}
+
 bool BrowserTestBase::UsingOSMesa() const {
   base::CommandLine* cmd = base::CommandLine::ForCurrentProcess();
   return cmd->GetSwitchValueASCII(switches::kUseGL) ==