WebUI: cr-search-field, do not call delegate if search query did not change.

ui/webui/resources/cr_elements/cr_search_field/cr_search_field_behavior.js

Index: ui/webui/resources/cr_elements/cr_search_field/cr_search_field_behavior.js
diff --git a/ui/webui/resources/cr_elements/cr_search_field/cr_search_field_behavior.js b/ui/webui/resources/cr_elements/cr_search_field/cr_search_field_behavior.js
index 3657f79f2600b74d83b7b4e4f754df3d87c44b32..a19adc25e0885fddc4848de0badadf5d21236d6d 100644
--- a/ui/webui/resources/cr_elements/cr_search_field/cr_search_field_behavior.js
+++ b/ui/webui/resources/cr_elements/cr_search_field/cr_search_field_behavior.js
@@ -38,6 +38,12 @@ var CrSearchFieldBehavior = {
     },
 
     hasSearchText: Boolean,
+
+    /** @private */
+    lastValue_: {
+      type: String,
+      value: '',
+    },
   },
 
   /**
@@ -74,9 +80,14 @@ var CrSearchFieldBehavior = {
   },
 
   onSearchTermSearch: function() {
-    this.hasSearchText = this.getValue() != '';
+    var newValue = this.getValue();
+    if (newValue == this.lastValue_)
+      return;
+
+    this.hasSearchText = newValue != '';
     if (this.delegate_)
-      this.delegate_.onSearchTermSearch(this.getValue());
+      this.delegate_.onSearchTermSearch(newValue);
+    this.lastValue_ = newValue;
   },
 
   onSearchTermKeydown: function(e) {