Fixes microsoft#8794

src/vs/workbench/parts/html/browser/webview.ts

@@ -8,9 +8,11 @@
 import URI from 'vs/base/common/uri';
 import {TPromise} from 'vs/base/common/winjs.base';
 import {IDisposable, dispose} from 'vs/base/common/lifecycle';
-import {addDisposableListener, addClass} from 'vs/base/browser/dom';
+import {addDisposableListener, addClass, EventType} from 'vs/base/browser/dom';
 import {isLightTheme, isDarkTheme} from 'vs/platform/theme/common/themes';
 import {KeybindingsRegistry} from 'vs/platform/keybinding/common/keybindingsRegistry';
+import {StandardKeyboardEvent} from 'vs/base/browser/keyboardEvent';
+import {KeyMod, KeyCode} from 'vs/base/common/keyCodes';
 
 declare interface WebviewElement extends HTMLElement {
 	src: string;
@@ -45,6 +47,19 @@ KeybindingsRegistry.registerCommandDesc({
 
 type ApiThemeClassName = 'vscode-light' | 'vscode-dark' | 'vscode-high-contrast';
 
+function isDefaultKeyboardEvent(e: KeyboardEvent): boolean {
+	let keyEvent = new StandardKeyboardEvent(e);
+	let keybinding = keyEvent.asKeybinding();
+	switch (keybinding) {
+		case KeyMod.CtrlCmd | KeyCode.KEY_C:
+		case KeyMod.CtrlCmd | KeyCode.KEY_V:
+		case KeyMod.CtrlCmd | KeyCode.KEY_X:
+		case KeyMod.CtrlCmd | KeyCode.KEY_A:
+			return true;
+	}
+	return false;
+}
+
 export default class Webview {
 
 	private _webview: WebviewElement;
@@ -93,6 +108,17 @@ export default class Webview {
 					this._webview.style.opacity = '';
 					return;
 				}
+			}),
+			addDisposableListener(this._webview, EventType.KEY_DOWN, (event: KeyboardEvent) => {
+				if (isDefaultKeyboardEvent(event)) {
+					event.stopImmediatePropagation();
+				}
+			}),
+			addDisposableListener(this._webview, EventType.DRAG_OVER, (event: DragEvent) => {
+				event.stopImmediatePropagation();
+			}),
+			addDisposableListener(this._webview, EventType.DROP, (event: DragEvent) => {
+				event.stopImmediatePropagation();
 			})
 		];