test: Fail CDP commands on unhandled exceptions

Install a Chrome Devtools Protocol handler for unhandled exceptions, and
fail the next CDP command with it.

This got lost with the move from PhantomJS to Chrome.

test/common/cdp-driver.js

@@ -61,6 +61,7 @@ function success(result) {
 var messages = [];
 var logPromiseResolver;
 var nReportedLogMessages = 0;
+var unhandledExceptions = [];
 
 function setupLogging(client) {
     client.Runtime.enable();
@@ -72,6 +73,8 @@ function setupLogging(client) {
         resolveLogPromise();
     });
 
+    client.Runtime.exceptionThrown(info => unhandledExceptions.push(info.exceptionDetails));
+
     client.Log.enable();
     client.Log.entryAdded(entry => {
         let msg = entry["entry"];
@@ -288,7 +291,14 @@ CDP.New(options)
                                 pageLoadPromise = new Promise((resolve, reject) => { pageLoadResolve = resolve; pageLoadReject = reject; });
 
                             // run the command
-                            eval(command).then(success, fail);
+                            eval(command).then(reply => {
+                                    if (unhandledExceptions.length === 0) {
+                                        success(reply);
+                                    } else {
+                                        fail(unhandledExceptions[0].exception.description);
+                                        unhandledExceptions.length = 0;
+                                    }
+                                }, fail);
 
                             input_buf = input_buf.slice(i+1);
                         }