Add background with rounded corners.

Will be used to implement a scrollview that does not extend beyond the
boundaries of a widget with rounded corners. Necessary because
scrollviews paint on a layer so they will paint over the parent view's
bounds. Also similar code creating rounded backgrounds happens in a
bunch of places in the codebase and could be simplified to use a single
common background factory method (example: bubble background code).

Change-Id: Ie885ca9f71f2722680e6fb709fe3091e71ad88fd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1524910
Commit-Queue: Sajad Maysam <sajadm@google.com>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Cr-Commit-Position: refs/heads/master@{#644468}

ui/views/background.cc

@@ -8,6 +8,7 @@
 #include "base/macros.h"
 #include "base/scoped_observer.h"
 #include "build/build_config.h"
+#include "cc/paint/paint_flags.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/color_palette.h"
 #include "ui/gfx/color_utils.h"
@@ -39,6 +40,28 @@ class SolidBackground : public Background {
   DISALLOW_COPY_AND_ASSIGN(SolidBackground);
 };
 
+// RoundedRectBackground is a filled solid colored background that has
+// rounded corners.
+class RoundedRectBackground : public Background {
+ public:
+  RoundedRectBackground(SkColor color, float radius) : radius_(radius) {
+    SetNativeControlColor(color);
+  }
+
+  void Paint(gfx::Canvas* canvas, View* view) const override {
+    cc::PaintFlags flags;
+    flags.setAntiAlias(true);
+    flags.setStyle(cc::PaintFlags::kFill_Style);
+    flags.setColor(get_color());
+    canvas->DrawRoundRect(gfx::RectF(view->GetLocalBounds()), radius_, flags);
+  }
+
+ private:
+  float radius_;
+
+  DISALLOW_COPY_AND_ASSIGN(RoundedRectBackground);
+};
+
 // ThemedSolidBackground is a solid background that stays in sync with a view's
 // native theme.
 class ThemedSolidBackground : public SolidBackground, public ViewObserver {
@@ -97,6 +120,11 @@ std::unique_ptr<Background> CreateSolidBackground(SkColor color) {
   return std::make_unique<SolidBackground>(color);
 }
 
+std::unique_ptr<Background> CreateRoundedRectBackground(SkColor color,
+                                                        float radius) {
+  return std::make_unique<RoundedRectBackground>(color, radius);
+}
+
 std::unique_ptr<Background> CreateThemedSolidBackground(
     View* view,
     ui::NativeTheme::ColorId color_id) {

ui/views/background.h

@@ -67,6 +67,11 @@ class VIEWS_EXPORT Background {
 // Creates a background that fills the canvas in the specified color.
 VIEWS_EXPORT std::unique_ptr<Background> CreateSolidBackground(SkColor color);
 
+// Creates a background that fills the canvas with rounded corners.
+VIEWS_EXPORT std::unique_ptr<Background> CreateRoundedRectBackground(
+    SkColor color,
+    float radius);
+
 // Creates a background that fills the canvas in the color specified by the
 // view's NativeTheme and the given color identifier.
 VIEWS_EXPORT std::unique_ptr<Background> CreateThemedSolidBackground(