MD Search Field: Properly respond to external changes to search value.

ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar_search_field.js

Index: ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar_search_field.js
diff --git a/ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar_search_field.js b/ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar_search_field.js
index 1036e4996952dc53524bf62904c73140ab7dd0f4..69f7d8efea827e83b99f64137e49376f762c4da0 100644
--- a/ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar_search_field.js
+++ b/ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar_search_field.js
@@ -26,10 +26,14 @@ Polymer({
       type: Boolean,
       reflectToAttribute: true
     },
+
+    /** @private */
+    hasSearchText_: Boolean,
   },
 
   listeners: {
     'tap': 'showSearch_',
+    'searchInput.bind-value-changed': 'onBindValueChanged_',
   },
 
   /**
@@ -53,18 +57,21 @@ Polymer({
 
   /** @private */
   onInputBlur_: function() {
-    if (!this.hasSearchText)
+    if (!this.hasSearchText_)
       this.showingSearch = false;
   },
 
   /**
-   * Expand the search field when a key is pressed with it focused. This ensures
-   * it can be used correctly by tab-focusing. 'keypress' is used instead of
-   * 'keydown' to avoid expanding on non-text keys (shift, escape, etc).
+   * Update the state of the search field whenever the underlying input value
+   * changes. Unlike onsearch or onkeypress, this is reliably called immediately
+   * after any change, whether the result of user input or JS modification.
    * @private
    */
-  onSearchTermKeypress_: function() {
-    this.showingSearch = true;
+  onBindValueChanged_: function() {
+    var newValue = this.$.searchInput.bindValue;
+    this.hasSearchText_ = newValue != '';
+    if (newValue != '')
+      this.showingSearch = true;
   },
 
   /**