PPAPI: Add an API for setting a custom user agent for URL requests.

ppapi/shared_impl/ppb_url_request_info_shared.cc

Index: ppapi/shared_impl/ppb_url_request_info_shared.cc
diff --git a/ppapi/shared_impl/ppb_url_request_info_shared.cc b/ppapi/shared_impl/ppb_url_request_info_shared.cc
index d7a3ea211746ba8f2922140b95158d8542e31728..058b2be0be5f71c1e9103717a92f62028d1dbc58 100644
--- a/ppapi/shared_impl/ppb_url_request_info_shared.cc
+++ b/ppapi/shared_impl/ppb_url_request_info_shared.cc
@@ -62,6 +62,8 @@ PPB_URLRequestInfo_Data::PPB_URLRequestInfo_Data()
       allow_credentials(false),
       has_custom_content_transfer_encoding(false),
       custom_content_transfer_encoding(),
+      has_custom_user_agent(false),
+      custom_user_agent(),
       prefetch_buffer_upper_threshold(kDefaultPrefetchBufferUpperThreshold),
       prefetch_buffer_lower_threshold(kDefaultPrefetchBufferLowerThreshold),
       body() {
@@ -181,6 +183,10 @@ bool PPB_URLRequestInfo_Shared::SetUndefinedProperty(
       data_.has_custom_content_transfer_encoding = false;
       data_.custom_content_transfer_encoding = std::string();
       return true;
+    case PP_URLREQUESTPROPERTY_CUSTOMUSERAGENT:
+      data_.has_custom_user_agent = false;
+      data_.custom_user_agent = std::string();
+      return true;
     default:
       return false;
   }
@@ -258,6 +264,10 @@ bool PPB_URLRequestInfo_Shared::SetStringProperty(
       data_.has_custom_content_transfer_encoding = true;
       data_.custom_content_transfer_encoding = value;
       return true;
+    case PP_URLREQUESTPROPERTY_CUSTOMUSERAGENT:
+      data_.has_custom_user_agent = true;
+      data_.custom_user_agent = value;
+      return true;
     default:
       return false;
   }