Fix crash in chrome://proximity-auth when executing JS with uninitialized page.

This fix initializes members that cause JS to be executed only upon receiving a
message from the page inidicating it is initialized.

BUG=516625
TEST=manual

Review URL: https://codereview.chromium.org/1299453002

Cr-Commit-Position: refs/heads/master@{#343965}

3 files changed, 21 insertions, 10 deletions

diff --git a/components/proximity_auth/webui/proximity_auth_webui_handler.cc b/components/proximity_auth/webui/proximity_auth_webui_handler.cc
index da5f19b..228cb94 100644
--- a/components/proximity_auth/webui/proximity_auth_webui_handler.cc
+++ b/components/proximity_auth/webui/proximity_auth_webui_handler.cc
@@ -131,6 +131,11 @@ ProximityAuthWebUIHandler::~ProximityAuthWebUIHandler() {
 
 void ProximityAuthWebUIHandler::RegisterMessages() {
   web_ui()->RegisterMessageCallback(
+      "onWebContentsInitialized",
+      base::Bind(&ProximityAuthWebUIHandler::OnWebContentsInitialized,
+                 base::Unretained(this)));
+
+  web_ui()->RegisterMessageCallback(
       "clearLogBuffer", base::Bind(&ProximityAuthWebUIHandler::ClearLogBuffer,
                                    base::Unretained(this)));
 
@@ -168,16 +173,6 @@ void ProximityAuthWebUIHandler::RegisterMessages() {
       "toggleConnection",
       base::Bind(&ProximityAuthWebUIHandler::ToggleConnection,
                  base::Unretained(this)));
-
-  InitGCMManager();
-  InitEnrollmentManager();
-  InitDeviceManager();
-
-  // Note: We add the observer for the logs after initializing the managers
-  // because when this function is called, the WebUI's underlying WebContents
-  // has not been initialized, so calling any JavaScript function will crash
-  // Chrome.
-  LogBuffer::GetInstance()->AddObserver(this);
 }
 
 void ProximityAuthWebUIHandler::OnLogMessageAdded(
@@ -233,6 +228,16 @@ void ProximityAuthWebUIHandler::OnSyncFinished(
   }
 }
 
+void ProximityAuthWebUIHandler::OnWebContentsInitialized(
+    const base::ListValue* args) {
+  if (!gcm_manager_ || !enrollment_manager_ || !device_manager_) {
+    InitGCMManager();
+    InitEnrollmentManager();
+    InitDeviceManager();
+    LogBuffer::GetInstance()->AddObserver(this);
+  }
+}
+
 void ProximityAuthWebUIHandler::GetLogMessages(const base::ListValue* args) {
   base::ListValue json_logs;
   for (const auto& log : *LogBuffer::GetInstance()->logs()) {
diff --git a/components/proximity_auth/webui/proximity_auth_webui_handler.h b/components/proximity_auth/webui/proximity_auth_webui_handler.h
index 1f87687..a6667b0 100644
--- a/components/proximity_auth/webui/proximity_auth_webui_handler.h
+++ b/components/proximity_auth/webui/proximity_auth_webui_handler.h
@@ -70,6 +70,7 @@ class ProximityAuthWebUIHandler : public content::WebUIMessageHandler,
       CryptAuthDeviceManager::DeviceChangeResult device_change_result) override;
 
   // Message handler callbacks.
+  void OnWebContentsInitialized(const base::ListValue* args);
   void GetLogMessages(const base::ListValue* args);
   void ClearLogBuffer(const base::ListValue* args);
   void ToggleUnlockKey(const base::ListValue* args);
diff --git a/components/proximity_auth/webui/resources/cryptauth_interface.js b/components/proximity_auth/webui/resources/cryptauth_interface.js
index 4e22c38..a7dbdb7 100644
--- a/components/proximity_auth/webui/resources/cryptauth_interface.js
+++ b/components/proximity_auth/webui/resources/cryptauth_interface.js
@@ -98,3 +98,8 @@ CryptAuthInterface = {
     });
   },
 };
+
+// This message tells the native WebUI handler that the WebContents backing the
+// WebUI has been iniitalized. This signal allows the native handler to execute
+// JavaScript inside the page.
+chrome.send('onWebContentsInitialized');