Do not SchedulePaint() inside views::Label::OnPaint()

ui/views/controls/label.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/views/controls/label.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <cmath>
@@ skipping 315 matching lines @@
   if (ShouldShowDefaultTooltip()) {
     // Note that |render_text_| is never elided (see the comment in Init() too).
     tooltip->assign(render_text_->GetDisplayText());
     return true;
   }
 
   return false;
 }
 
 void Label::OnEnabledChanged() {
-  RecalculateColors();
+  ApplyTextColors();
+  View::OnEnabledChanged();
 }
 
 std::unique_ptr<gfx::RenderText> Label::CreateRenderText(
     const base::string16& text,
     gfx::HorizontalAlignment alignment,
     gfx::DirectionalityMode directionality,
     gfx::ElideBehavior elide_behavior) {
   std::unique_ptr<gfx::RenderText> render_text(
       render_text_->CreateInstanceOfSameType());
   render_text->SetHorizontalAlignment(alignment);
   render_text->SetDirectionalityMode(directionality);
   render_text->SetElideBehavior(elide_behavior);
   render_text->SetObscured(obscured());
   render_text->SetMinLineHeight(line_height());
   render_text->SetFontList(font_list());
   render_text->set_shadows(shadows());
   render_text->SetCursorEnabled(false);
   render_text->SetText(text);
   return render_text;
 }
 
 void Label::PaintText(gfx::Canvas* canvas) {
   MaybeBuildRenderTextLines();

[tapted, 2016/06/14 11:15:54]

This was the call triggering a second paint

   for (size_t i = 0; i < lines_.size(); ++i)
     lines_[i]->Draw(canvas);
 }
 
 void Label::OnBoundsChanged(const gfx::Rect& previous_bounds) {
   if (previous_bounds.size() != size())
     InvalidateLayout();
 }
 
 void Label::OnPaint(gfx::Canvas* canvas) {
@@ skipping 105 matching lines @@
       std::unique_ptr<gfx::RenderText> line =
           CreateRenderText(lines[i], alignment, directionality, elide_behavior);
       line->SetDisplayRect(rect);
       lines_.push_back(std::move(line));
       rect.set_y(rect.y() + rect.height());
     }
     // Append the remaining text to the last visible line.
     for (size_t i = lines_.size(); i < lines.size(); ++i)
       lines_.back()->SetText(lines_.back()->text() + lines[i]);
   }
-  RecalculateColors();
+  ApplyTextColors();
 }
 
 gfx::Rect Label::GetFocusBounds() {
   MaybeBuildRenderTextLines();

[tapted, 2016/06/14 11:15:54]

There's a call here as well, but GetFocusBounds() is only called in OnPaint.
(the only other call is in GetDisplayTextForTesting())

 
   gfx::Rect focus_bounds;
   if (lines_.empty()) {
     focus_bounds = gfx::Rect(GetTextSize());
   } else {
     for (size_t i = 0; i < lines_.size(); ++i) {
       gfx::Point origin;
       origin += lines_[i]->GetLineOffset(0);
       focus_bounds.Union(gfx::Rect(origin, lines_[i]->GetStringSize()));
     }
@@ skipping 54 matching lines @@
 void Label::RecalculateColors() {
   actual_enabled_color_ = auto_color_readability_ ?
       color_utils::GetReadableColor(requested_enabled_color_,
                                     background_color_) :
       requested_enabled_color_;
   actual_disabled_color_ = auto_color_readability_ ?
       color_utils::GetReadableColor(requested_disabled_color_,
                                     background_color_) :
       requested_disabled_color_;
 
+  ApplyTextColors();
+  SchedulePaint();
+}
+
+void Label::ApplyTextColors() {
   SkColor color = enabled() ? actual_enabled_color_ : actual_disabled_color_;
   bool subpixel_rendering_suppressed =
       SkColorGetA(background_color_) != 0xFF || !subpixel_rendering_enabled_;
   for (size_t i = 0; i < lines_.size(); ++i) {
     lines_[i]->SetColor(color);
     lines_[i]->set_subpixel_rendering_suppressed(subpixel_rendering_suppressed);
   }
-  SchedulePaint();
 }
 
 void Label::UpdateColorsFromTheme(const ui::NativeTheme* theme) {
   if (!enabled_color_set_) {
     requested_enabled_color_ = theme->GetSystemColor(
         ui::NativeTheme::kColorId_LabelEnabledColor);
   }
   if (!disabled_color_set_) {
     requested_disabled_color_ = theme->GetSystemColor(
         ui::NativeTheme::kColorId_LabelDisabledColor);
   }
   if (!background_color_set_) {
     background_color_ = theme->GetSystemColor(
         ui::NativeTheme::kColorId_LabelBackgroundColor);
   }
   RecalculateColors();
 }
 
 bool Label::ShouldShowDefaultTooltip() const {
   const gfx::Size text_size = GetTextSize();
   const gfx::Size size = GetContentsBounds().size();
   return !obscured() && (text_size.width() > size.width() ||
                          (multi_line() && text_size.height() > size.height()));
 }
 
 }  // namespace views