Compile core/paint/ with -Wshadow.

Bug: 294205
Change-Id: Ia27612e37a3d5c944a0d8ef3bf3af5250cf508ff
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2462263Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org>
Commit-Queue: Morten Stenshorne <mstensho@chromium.org>
Cr-Commit-Position: refs/heads/master@{#815636}

third_party/blink/renderer/core/paint/BUILD.gn

@@ -5,6 +5,8 @@
 import("//third_party/blink/renderer/core/core.gni")
 
 blink_core_sources("paint") {
+  configs += [ "//build/config/compiler:noshadowing" ]
+
   sources = [
     "applied_decoration_painter.cc",
     "applied_decoration_painter.h",

third_party/blink/renderer/core/paint/compositing/graphics_layer_updater.cc

@@ -165,9 +165,9 @@ void GraphicsLayerUpdater::UpdateRecursive(
     // If we have a forced update, we notify the display lock to ensure that the
     // forced update resumes after the lock has been removed.
     if (update_type == kForceUpdate) {
-      auto* context = layer.GetLayoutObject().GetDisplayLockContext();
-      DCHECK(context);
-      context->NotifyForcedGraphicsLayerUpdateBlocked();
+      auto* child_context = layer.GetLayoutObject().GetDisplayLockContext();
+      DCHECK(child_context);
+      child_context->NotifyForcedGraphicsLayerUpdateBlocked();
     }
   }
 

third_party/blink/renderer/core/paint/inline_text_box_painter.cc

@@ -420,7 +420,7 @@ void InlineTextBoxPainter::Paint(const PaintInfo& paint_info,
     // the first time, we draw the glyphs outside the selection area, with
     // the original style.
     {
-      GraphicsContextStateSaver state_saver(context);
+      GraphicsContextStateSaver inner_state_saver(context);
       context.ClipOut(FloatRect(selection_rect));
       text_painter.Paint(selection_start, selection_end, length, text_style,
                          node_id);
@@ -428,7 +428,7 @@ void InlineTextBoxPainter::Paint(const PaintInfo& paint_info,
     // the second time, we draw the glyphs inside the selection area, with
     // the selection style.
     {
-      GraphicsContextStateSaver state_saver(context);
+      GraphicsContextStateSaver inner_state_saver(context);
       context.Clip(FloatRect(selection_rect));
       text_painter.Paint(selection_start, selection_end, length,
                          selection_style, node_id);