Use correct TabLaunchType for context menu in Chrome Shell

Changing TabLaunchType from FROM_LINK to FROM_LONGPRESS_FOREGROUND. This should
not have any functionality impact, it's just more correct.

BUG=465329

Review URL: https://codereview.chromium.org/991823003

Cr-Commit-Position: refs/heads/master@{#319626}

chrome/android/shell/java/src/org/chromium/chrome/shell/ChromeShellTab.java

@@ -97,12 +97,12 @@ public class ChromeShellTab extends Tab {
         return new ChromeContextMenuPopulator(new TabChromeContextMenuItemDelegate() {
             @Override
             public void onOpenInNewTab(String url, Referrer referrer) {
-                mTabManager.createTab(url, TabLaunchType.FROM_LINK);
+                mTabManager.createTab(url, TabLaunchType.FROM_LONGPRESS_FOREGROUND);
             }
 
             @Override
             public void onOpenImageInNewTab(String url, Referrer referrer) {
-                mTabManager.createTab(url, TabLaunchType.FROM_LINK);
+                mTabManager.createTab(url, TabLaunchType.FROM_LONGPRESS_FOREGROUND);
             }
         });
     }