issue 102 Do something reasonable if the Stylish DB can't be read

_locales/en/messages.json

@@ -72,6 +72,10 @@
 		"message": "Checking...",
 		"description": "Text to display when checking a style for an update"
 	},
+	"dbError": {
+		"message": "An error has occurred using the Stylish database. Would you like to visit a web page with possible solutions?",
+		"description": "Prompt when a DB error is encountered"
+	},
 	"deleteStyleLabel": {
 		"message": "Delete",
 		"description": "Label for the button to delete a style"

background.js

@@ -21,6 +21,9 @@ chrome.extension.onMessage.addListener(function(request, sender, sendResponse) {
 		case "styleChanged":
 			cachedStyles = null;
 			break;
+		case "healthCheck":
+			getDatabase(function() { sendResponse(true); }, function() { sendResponse(false); });
+			break;
 	}
 });
 

health.js

@@ -0,0 +1,7 @@
+chrome.extension.sendMessage({method: "healthCheck"}, function(ok) {
+	if (!ok) {
+		if (confirm(t("dbError"))) {
+			window.open("http://userstyles.org/dberror");
+		}
+	}
+});

manage.html

@@ -85,6 +85,7 @@
 			}
 		</style>
 		<script src="localization.js"></script>
+		<script src="health.js"></script>
 		<script src="storage.js"></script>
 		<script src="messaging.js"></script>
 	</head>

popup.html

@@ -39,6 +39,7 @@
 		</style>
 
 		<script src="localization.js"></script>
+		<script src="health.js"></script>
 		<script src="storage.js"></script>
 		<script src="messaging.js"></script>
 </head>

storage.js

@@ -4,7 +4,12 @@ function getDatabase(ready, error) {
 		ready(stylishDb);
 		return;
 	}
+	try {
 		stylishDb = openDatabase('stylish', '', 'Stylish Styles', 5*1024*1024);
+	} catch (ex) {
+		error();
+		throw ex;
+	}
 	if (stylishDb.version == "1.0" || stylishDb.version == "") {
 		dbV11(stylishDb, error, ready);
 	} else if (stylishDb.version == "1.1") {