Check the available storage size before starting encryption migration.

chrome/browser/resources/chromeos/login/encryption_migration.js

Index: chrome/browser/resources/chromeos/login/encryption_migration.js
diff --git a/chrome/browser/resources/chromeos/login/encryption_migration.js b/chrome/browser/resources/chromeos/login/encryption_migration.js
index 86f8e435979b40c9e6a6e29f20f7e827177738fd..0004af3d28ccbc9d7835c016499ff1260fbd3e06 100644
--- a/chrome/browser/resources/chromeos/login/encryption_migration.js
+++ b/chrome/browser/resources/chromeos/login/encryption_migration.js
@@ -14,9 +14,11 @@
  */
 var EncryptionMigrationUIState = {
   INITIAL: 0,
-  MIGRATING: 1,
-  MIGRATION_SUCCEEDED: 2,
-  MIGRATION_FAILED: 3
+  READY: 1,
+  MIGRATING: 2,
+  MIGRATION_SUCCEEDED: 3,
+  MIGRATION_FAILED: 4,
+  NOT_ENOUGH_SPACE: 5
 };
 
 Polymer({
@@ -52,6 +54,15 @@ Polymer({
   },
 
   /**
+   * Returns true if the migration is ready to start.
+   * @param {EncryptionMigrationUIState} state Current UI state
+   * @private
+   */
+  isReady_: function(state) {
+    return state == EncryptionMigrationUIState.READY;
+  },
+
+  /**
    * Returns true if the migration is in progress.
    * @param {EncryptionMigrationUIState} state Current UI state
    * @private
@@ -79,6 +90,15 @@ Polymer({
   },
 
   /**
+   * Returns true if the available space is not enough to start migration.
+   * @param {EncryptionMigrationUIState} state Current UI state
+   * @private
+   */
+  isNotEnoughSpace_: function(state) {
+    return state == EncryptionMigrationUIState.NOT_ENOUGH_SPACE;
+  },
+
+  /**
    * Returns true if the current migration progress is unknown.
    * @param {number} progress
    * @private