Make the webstore inline install dialog be tab-modal

Also clean up a few minor lint errors while I'm in here.

BUG=550047

Review URL: https://codereview.chromium.org/1496033003

Cr-Commit-Position: refs/heads/master@{#363925}
void ShowExtensionInstallDialogImpl(
    ExtensionInstallPromptShowParams* show_params,
    ExtensionInstallPrompt::Delegate* delegate,
    scoped_refptr<ExtensionInstallPrompt::Prompt> prompt) {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  ExtensionInstallDialogView* dialog =
      new ExtensionInstallDialogView(show_params->profile(),
                                      show_params->GetParentWebContents(),
                                      delegate,
                                      prompt);
  if (prompt->ShouldUseTabModalDialog()) {
    content::WebContents* parent_web_contents =
        show_params->GetParentWebContents();
    if (parent_web_contents)
      constrained_window::ShowWebModalDialogViews(dialog, parent_web_contents);
  } else {
    constrained_window::CreateBrowserModalDialogViews(
        dialog, show_params->GetParentWindow())
        ->Show();
  }
 }

void ShowExtensionInstallDialogImpl(
    ExtensionInstallPromptShowParams* show_params,
    ExtensionInstallPrompt::Delegate* delegate,
    scoped_refptr<ExtensionInstallPrompt::Prompt> prompt) {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  ExtensionInstallDialogView* dialog =
      new ExtensionInstallDialogView(show_params->profile(),
                                      show_params->GetParentWebContents(),
                                      delegate,
                                      prompt);
  constrained_window::CreateBrowserModalDialogViews(
      dialog, show_params->GetParentWindow())->Show();
 }
