[Favicon] Add new fallback icon rendering flow.

components/favicon_base/favicon_types.cc

Index: components/favicon_base/favicon_types.cc
diff --git a/components/favicon_base/favicon_types.cc b/components/favicon_base/favicon_types.cc
index eb0e7bcfa6b0a662720117c33c24ff5abd1b43de..033c7a2ef627bb1e1d677dce8dda190d6547f36a 100644
--- a/components/favicon_base/favicon_types.cc
+++ b/components/favicon_base/favicon_types.cc
@@ -3,17 +3,38 @@
 // found in the LICENSE file.
 
 #include "components/favicon_base/favicon_types.h"
+#include "ui/gfx/color_utils.h"
 
 namespace favicon_base {
 
-// FaviconImageResult ---------------------------------------------------------
+namespace {
+
+// Luminance threshold for background color determine whether to use dark or
+// light text color.
+int kDarkTextLuminanceThreshold = 190;
+
+// Default values for FallbackIconStyle.
+SkColor kDefaultBackgroundColor = SkColorSetRGB(0x80, 0x80, 0x80);
+SkColor kDefaultTextColorDark = SK_ColorBLACK;
+SkColor kDefaultTextColorLight = SK_ColorWHITE;
+double kDefaultFontSizeRatio = 0.8;
+double kDefaultRoundness = 0.125;  // 1 / 8.
+
+// Bounds for mebers of FallbackIconStyle;
+double kMaxFontSizeRatio = 1.0;
+double kMaxRoundness = 1.0;

[pkotwicz, 2015/01/23 16:00:48]

Nit: Remove these. It does not make sense to have a constant for the maximum but
not for the minimum

[huangs, 2015/01/23 19:47:52]

Removed.

+
+}  // namespace
+
+// ---------------------------------------------------------
+// FaviconImageResult
 
 FaviconImageResult::FaviconImageResult() {}
 
 FaviconImageResult::~FaviconImageResult() {}
 
-// FaviconRawBitmapResult
 // --------------------------------------------------------
+// FaviconRawBitmapResult
 
 FaviconRawBitmapResult::FaviconRawBitmapResult()
     : expired(false), icon_type(INVALID_ICON) {
@@ -22,4 +43,28 @@ FaviconRawBitmapResult::FaviconRawBitmapResult()
 FaviconRawBitmapResult::~FaviconRawBitmapResult() {
 }
 
-}  // namespace chrome
+// --------------------------------------------------------
+// FallbackIconStyle
+
+FallbackIconStyle::FallbackIconStyle()
+    : background_color(kDefaultBackgroundColor),
+      text_color(kDefaultTextColorLight),
+      font_size_ratio(kDefaultFontSizeRatio),
+      roundness(kDefaultRoundness) {
+}
+
+FallbackIconStyle::~FallbackIconStyle() {
+}
+
+void FallbackIconStyle::MatchTextColorWithBackgroundColor() {

[pkotwicz, 2015/01/23 16:00:48]

Optional: color_utils::GetReadableColor(SK_ColorBLACK, background_color) yields
the same result. It is probably better to use that

[huangs, 2015/01/23 19:47:52]

I just tried this, and got
background #757575 or darker  => white text
background #767676 or lighter => black text

In particular, we want default background #808080 to have *white* text.  So we
need to use the old wan and control the threshold ourselves.  :(  No change in
code.

+  int luminance = color_utils::GetLuminanceForColor(background_color);
+  text_color = (luminance >= kDarkTextLuminanceThreshold ?
+      kDefaultTextColorDark : kDefaultTextColorLight);
+}
+
+bool FallbackIconStyle::is_valid() const {
+  return font_size_ratio >= 0.0 && font_size_ratio <= kMaxFontSizeRatio
+      && roundness >= 0.0 && roundness <= kMaxRoundness;

[pkotwicz, 2015/01/23 16:00:48]

Style: && goes on the previous line

[huangs, 2015/01/23 19:47:52]

Done.

+}
+
+}  // namespace favicon_base