Fix for unused-lambda-capture warning

This CL is part of
https://chromium-review.googlesource.com/c/chromium/src/+/1286017

This CL was uploaded by git cl split.

R=xdai@chromium.org

Bug: 681136
Change-Id: I2dff39578c1c05a5ddef7758b74a84f7b54b00af
Reviewed-on: https://chromium-review.googlesource.com/c/1288491Reviewed-by: Xiaoqian Dai <xdai@chromium.org>
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#601054}

chrome/browser/ui/ash/test_wallpaper_controller.cc

@@ -12,7 +12,7 @@ TestWallpaperController::~TestWallpaperController() = default;
 
 void TestWallpaperController::ShowWallpaperImage(const gfx::ImageSkia& image) {
   current_wallpaper = image;
-  test_observers_.ForAllPtrs([this](ash::mojom::WallpaperObserver* observer) {
+  test_observers_.ForAllPtrs([](ash::mojom::WallpaperObserver* observer) {
     observer->OnWallpaperChanged(dummy_image_id);
   });
 }