bluetooth: Add NetworkError for Bluetooth on browser side

Return the NetworkError if the connectGATT fails.

This is the second of two patches to implement NetworkError:
  [1] https://codereview.chromium.org/1124973003
  [2] This patch.

BUG=484779

Review URL: https://codereview.chromium.org/1118053003

Cr-Commit-Position: refs/heads/master@{#329512}

content/child/bluetooth/bluetooth_dispatcher.cc

@@ -39,6 +39,8 @@ int CurrentWorkerId() {
 WebBluetoothError::ErrorType WebBluetoothErrorFromBluetoothError(
     BluetoothError error_type) {
   switch (error_type) {
+    case BluetoothError::NETWORK_ERROR:
+      return WebBluetoothError::NetworkError;
     case BluetoothError::NOT_FOUND:
       return WebBluetoothError::NotFoundError;
     case BluetoothError::SECURITY:

content/common/bluetooth/bluetooth_error.h

@@ -9,7 +9,12 @@ namespace content {
 
 // Error enumerations corresponding to blink::WebBluetoothError::ErrorType
 // used to create DOMExceptions.
-enum class BluetoothError { NOT_FOUND, SECURITY, ENUM_MAX_VALUE = SECURITY };
+enum class BluetoothError {
+  NOT_FOUND,
+  NETWORK_ERROR,
+  SECURITY,
+  ENUM_MAX_VALUE = SECURITY
+};
 
 }  // namespace content