Make the popup blocker on by default. Flip the flag to be a disabling one.

chrome/browser/ui/cocoa/location_bar/content_setting_decoration.mm

Index: chrome/browser/ui/cocoa/location_bar/content_setting_decoration.mm
diff --git a/chrome/browser/ui/cocoa/location_bar/content_setting_decoration.mm b/chrome/browser/ui/cocoa/location_bar/content_setting_decoration.mm
index 523eb6fa82d8dc3dfcd419ed87f30305686a8e30..48abf2ef3c69ff337e1cae975267233a7ac750a2 100644
--- a/chrome/browser/ui/cocoa/location_bar/content_setting_decoration.mm
+++ b/chrome/browser/ui/cocoa/location_bar/content_setting_decoration.mm
@@ -188,8 +188,8 @@ bool ContentSettingDecoration::UpdateFromTabContents(
     bool has_animated_text =
         content_setting_image_model_->explanatory_string_id();
     // Check if the animation is enabled.
-    bool animation_enabled = CommandLine::ForCurrentProcess()->HasSwitch(
-        switches::kEnableBlockContentAnimation);
+    bool animation_enabled = !CommandLine::ForCurrentProcess()->HasSwitch(
+        switches::kDisableBlockContentAnimation);
     if (has_animated_text && animation_enabled && !animation_) {
       // Start animation, its timer will drive reflow. Note the text is
       // cached so it is not allowed to change during the animation.