feat: nicer protocol error messages (#2742)

This patch:
- stops appending `undefined` to our protocol messages unnecessarily.
- rewrites `Cannot find execution context id` to `Execution context was destroyed, most likely because of a navigation.` when it occurs from a Puppeteer ExecutionContext. The error message is left alone if it occurs via a CDPSession.

lib/ExecutionContext.js

@@ -64,13 +64,13 @@ class ExecutionContext {
     if (helper.isString(pageFunction)) {
       const contextId = this._contextId;
       const expression = /** @type {string} */ (pageFunction);
-      const { exceptionDetails, result: remoteObject } = await this._client.send('Runtime.evaluate', {
+      const {exceptionDetails, result: remoteObject} = await this._client.send('Runtime.evaluate', {
         expression,
         contextId,
         returnByValue: false,
         awaitPromise: true,
         userGesture: true
-      });
+      }).catch(rewriteError);
       if (exceptionDetails)
         throw new Error('Evaluation failed: ' + helper.getExceptionMessage(exceptionDetails));
       return this._objectHandleFactory(remoteObject);
@@ -83,7 +83,7 @@ class ExecutionContext {
       returnByValue: false,
       awaitPromise: true,
       userGesture: true
-    });
+    }).catch(rewriteError);
     if (exceptionDetails)
       throw new Error('Evaluation failed: ' + helper.getExceptionMessage(exceptionDetails));
     return this._objectHandleFactory(remoteObject);
@@ -116,6 +116,16 @@ class ExecutionContext {
       }
       return { value: arg };
     }
+
+    /**
+     * @param {!Error} error
+     * @return {!Protocol.Runtime.evaluateReturnValue}
+     */
+    function rewriteError(error) {
+      if (error.message.endsWith('Cannot find context with specified id'))
+        throw new Error('Execution context was destroyed, most likely because of a navigation.');
+      throw error;
+    }
   }
 
   /**