LibGfx: Use a bit of constexpr in Color

This avoids a bunch of strlen()'s when we're parsing web colors.

Libraries/LibGfx/Color.cpp

@@ -204,11 +204,16 @@ Optional<Color> Color::from_string(const StringView& string)
         return {};
 
     struct ColorAndWebName {
+        constexpr ColorAndWebName(RGBA32 c, const char* n)
+            : color(c)
+            , name(n)
+        {
+        }
         RGBA32 color;
-        const char* name;
+        StringView name;
     };
 
-    const ColorAndWebName web_colors[] = {
+    constexpr ColorAndWebName web_colors[] = {
         // CSS Level 1
         { 0x000000, "black" },
         { 0xc0c0c0, "silver" },
@@ -365,7 +370,7 @@ Optional<Color> Color::from_string(const StringView& string)
         { 0x000000, nullptr }
     };
 
-    for (size_t i = 0; web_colors[i].name; ++i) {
+    for (size_t i = 0; !web_colors[i].name.is_null(); ++i) {
         if (string == web_colors[i].name)
             return Color::from_rgb(web_colors[i].color);
     }

Libraries/LibGfx/Color.h

@@ -72,19 +72,19 @@ public:
         MidMagenta,
     };
 
-    Color() {}
+    constexpr Color() { }
     Color(NamedColor);
-    Color(u8 r, u8 g, u8 b)
+    constexpr Color(u8 r, u8 g, u8 b)
         : m_value(0xff000000 | (r << 16) | (g << 8) | b)
     {
     }
-    Color(u8 r, u8 g, u8 b, u8 a)
+    constexpr Color(u8 r, u8 g, u8 b, u8 a)
         : m_value((a << 24) | (r << 16) | (g << 8) | b)
     {
     }
 
-    static Color from_rgb(unsigned rgb) { return Color(rgb | 0xff000000); }
-    static Color from_rgba(unsigned rgba) { return Color(rgba); }
+    static constexpr Color from_rgb(unsigned rgb) { return Color(rgb | 0xff000000); }
+    static constexpr Color from_rgba(unsigned rgba) { return Color(rgba); }
 
     u8 red() const { return (m_value >> 16) & 0xff; }
     u8 green() const { return (m_value >> 8) & 0xff; }
@@ -267,7 +267,7 @@ public:
     }
 
 private:
-    explicit Color(RGBA32 rgba)
+    constexpr explicit Color(RGBA32 rgba)
         : m_value(rgba)
     {
     }