Truncate the Javascript alert message if the length is too long on Mac port

chrome/browser/ui/cocoa/javascript_app_modal_dialog_cocoa.mm

Index: chrome/browser/ui/cocoa/javascript_app_modal_dialog_cocoa.mm
diff --git a/chrome/browser/ui/cocoa/javascript_app_modal_dialog_cocoa.mm b/chrome/browser/ui/cocoa/javascript_app_modal_dialog_cocoa.mm
index 7341835b372e3527306b29bcf4a07474317b3d93..b66cb253e20417d117ce4c6391531e94bd0f32fd 100644
--- a/chrome/browser/ui/cocoa/javascript_app_modal_dialog_cocoa.mm
+++ b/chrome/browser/ui/cocoa/javascript_app_modal_dialog_cocoa.mm
@@ -17,6 +17,9 @@
 #include "ui/base/l10n/l10n_util_mac.h"
 #include "ui/base/ui_base_types.h"
 
+const int kSlotsPerLine = 50;
+const int kMessageTextMaxSlots = 2000;
+
 // Helper object that receives the notification that the dialog/sheet is
 // going away. Is responsible for cleaning itself up.
 @interface JavaScriptAppModalDialogHelper : NSObject<NSAlertDelegate> {
@@ -146,6 +149,30 @@ JavaScriptAppModalDialogCocoa::JavaScriptAppModalDialogCocoa(
   [alert_ setDelegate:helper_];
   NSString* informative_text =
       base::SysUTF16ToNSString(dialog_->message_text());
+
+  // Truncate long JS alerts - crbug.com/331219
+  NSArray* info_array =
+      [informative_text componentsSeparatedByCharactersInSet:
+          [NSCharacterSet newlineCharacterSet]];
+  informative_text = [[NSString alloc] init];

[Avi (use Gerrit), 2014/01/24 01:53:24]

This leaks. You can do

informative_text = @"";

+  int occupied_slots = 0;
+  for (NSString* info_text in info_array) {
+    int new_slots =
+        info_text.length < kSlotsPerLine ? kSlotsPerLine : info_text.length;

[Avi (use Gerrit), 2014/01/24 01:53:24]

std::max?

+    int free_slots = kMessageTextMaxSlots - occupied_slots;

[Avi (use Gerrit), 2014/01/24 01:53:24]

You recompute free_slots each time; easier is to make line 158:

int free_slots = kMessageTextMaxSlots;

drop this line, and then below on line 166 do:

free_slots -= new_slots;

+    if (free_slots >= new_slots) {
+      informative_text = [informative_text stringByAppendingString:info_text];
+      informative_text = [informative_text stringByAppendingString:@"\n"];
+      occupied_slots += new_slots;
+    } else {
+      if ((int)info_text.length > free_slots)

[Avi (use Gerrit), 2014/01/24 01:53:24]

Alleviate the need for a cast if you make free_slots a size_t.

+          info_text = [info_text substringToIndex:free_slots];

[Avi (use Gerrit), 2014/01/24 01:53:24]

Indent 2 for an if().

+      informative_text = [informative_text stringByAppendingString:info_text];
+      informative_text = [informative_text stringByAppendingString:@"\n..."];

[Avi (use Gerrit), 2014/01/24 01:53:24]

What bums me out is that we have gfx::TruncateString to do exactly this kind of
truncation. Can we be clever in counting to re-use it?

+      break;
+    }
+  }
+
   [alert_ setInformativeText:informative_text];
   NSString* message_text =
       base::SysUTF16ToNSString(dialog_->title());