Add viewing of error messages from Keystone upon self-update failure.

chrome/browser/ui/webui/help/version_updater_mac.mm

Index: chrome/browser/ui/webui/help/version_updater_mac.mm
diff --git a/chrome/browser/ui/webui/help/version_updater_mac.mm b/chrome/browser/ui/webui/help/version_updater_mac.mm
index be9c08fae51df9624654a2f48ced5f131d66cfcf..a12e3304d6580bf276c3fc6d5cfb45bce8f8ca16 100644
--- a/chrome/browser/ui/webui/help/version_updater_mac.mm
+++ b/chrome/browser/ui/webui/help/version_updater_mac.mm
@@ -6,6 +6,8 @@
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
+#include "base/strings/stringprintf.h"
+#include "base/strings/utf_string_conversions.h"
 #include "chrome/browser/lifetime/application_lifetime.h"
 #import "chrome/browser/mac/keystone_glue.h"
 #include "chrome/browser/obsolete_system/obsolete_system.h"
@@ -132,6 +134,8 @@ void VersionUpdaterMac::RelaunchBrowser() const {
 void VersionUpdaterMac::UpdateStatus(NSDictionary* dictionary) {
   AutoupdateStatus keystone_status = static_cast<AutoupdateStatus>(
       [[dictionary objectForKey:kAutoupdateStatusStatus] intValue]);
+  const char* keystone_errors_utf8 =
+      [[dictionary objectForKey:kAutoupdateStatusErrorMessages] UTF8String];
 
   bool enable_promote_button = true;
   base::string16 message;
@@ -211,6 +215,20 @@ void VersionUpdaterMac::UpdateStatus(NSDictionary* dictionary) {
       NOTREACHED();
       return;
   }
+
+  // If there are any specific error messages being passed along by Keystone,
+  // include them in a <pre> block.
+  if (!message.empty() &&
+      keystone_errors_utf8 && strlen(keystone_errors_utf8)) {
+    // TODO: Should we localize the "Error details" string?  If so, get the
+    // string translated and into GRD, then replace this StringPrintf call
+    // with a call to l10n_util::GetStringFUTF16(IDS_KEYSTONE_ERROR_DETAILS).
+    std::string formatted_errors =
+        base::StringPrintf("<br/><br/>Error details:<br/><pre>%s</pre>",
+                           keystone_errors_utf8);

[Boris Vidolov, 2016/03/08 22:32:52]

The code needs to sanitize the contents of keystone_errors_utf8. '<' and '>' are
common in the Keystone errors. I am not that familiar with the Chrome code base,
but I would assume that there is code for XML/HTML escaping/sanitization. 
If not, you can use the GTM code, which is already imported by Chrome with
-[NSString gtm_stringByEscapingForHTML]

+    message += base::UTF8ToUTF16(formatted_errors.c_str());
+  }
+
   if (!status_callback_.is_null())
     status_callback_.Run(status, 0, message);