Adds a test for setting empty composition text.

chrome/test/data/extensions/api_test/input_ime_nonchromeos/background.js

Index: chrome/test/data/extensions/api_test/input_ime_nonchromeos/background.js
diff --git a/chrome/test/data/extensions/api_test/input_ime_nonchromeos/background.js b/chrome/test/data/extensions/api_test/input_ime_nonchromeos/background.js
index 6f0b371a4bd39c2796d25394f8cc13846fca6281..18a89150162e363e1eb88e78dde5ddeb5774020d 100644
--- a/chrome/test/data/extensions/api_test/input_ime_nonchromeos/background.js
+++ b/chrome/test/data/extensions/api_test/input_ime_nonchromeos/background.js
@@ -83,6 +83,19 @@ chrome.test.runTests([
       chrome.test.succeed();
     });
   },
+  function testEmptyComposition() {
+    chrome.input.ime.setComposition({
+      contextID: 1,
+      text: '',
+      cursor: 0
+    }, function() {
+      if(chrome.runtime.lastError) {
+        chrome.test.fail();
+        return;
+      }
+      chrome.test.succeed();
+    });
+  },
   // Test input.ime.sendKeyEvents API.
   function testSendKeyEvents() {
     // Sends a normal character key.