Move DocumentTabModelSelector and related classes upstream

chrome/android/java/src/org/chromium/chrome/browser/document/BrandColorUtils.java

Index: chrome/android/java/src/org/chromium/chrome/browser/document/BrandColorUtils.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/document/BrandColorUtils.java b/chrome/android/java/src/org/chromium/chrome/browser/document/BrandColorUtils.java
new file mode 100644
index 0000000000000000000000000000000000000000..1333ed4059e856a2de49b490dfa09ab0385e8dc8
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/document/BrandColorUtils.java
@@ -0,0 +1,76 @@
+// Copyright 2014 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.
+
+package org.chromium.chrome.browser.document;
+
+import android.graphics.Color;
+
+/**
+ * Utilities for brand color related properties.
+ */
+public class BrandColorUtils {
+    private static final float CONTRAST_LIGHT_TEXT_THRESHOLD = 3f;
+    private static final float LIGHTNESS_OPAQUE_BOX_THRESHOLD = 0.82f;
+
+    /** Percentage to darken the brand color by when setting the status bar color. */
+    private static final float DARKEN_COLOR_FRACTION = 0.6f;
+
+    /**
+     * Computes the lightness value in HSL standard for the given color.
+     */
+    private static float getLightnessForColor(int color) {
+        int red = Color.red(color);
+        int green = Color.green(color);
+        int blue = Color.blue(color);
+        int largest = Math.max(red, Math.max(green, blue));
+        int smallest = Math.min(red, Math.min(green, blue));
+        int average = (largest + smallest) / 2;
+        return average / 255.0f;
+    }
+
+    /** Calculates the contrast between the given color and white, using the algorithm provided by
+     * the WCAG v2 in http://www.w3.org/TR/WCAG20/#contrast-ratiodef.
+     */
+    private static float getContrastForColor(int color) {
+        float bgR = Color.red(color) / 255f;
+        float bgG = Color.green(color) / 255f;
+        float bgB = Color.blue(color) / 255f;
+        bgR = (bgR < 0.03928f) ? bgR / 12.92f : (float) Math.pow((bgR + 0.055f) / 1.055f, 2.4f);
+        bgG = (bgG < 0.03928f) ? bgG / 12.92f : (float) Math.pow((bgG + 0.055f) / 1.055f, 2.4f);
+        bgB = (bgB < 0.03928f) ? bgB / 12.92f : (float) Math.pow((bgB + 0.055f) / 1.055f, 2.4f);
+        float bgL = 0.2126f * bgR + 0.7152f * bgG + 0.0722f * bgB;
+        return Math.abs((1.05f) / (bgL + 0.05f));
+    }
+
+    /**
+     * Darkens the given color to use on the status bar.
+     * @param color Brand color of the website.
+     * @return Color that should be used for Android status bar.
+     */
+    public static int computeStatusBarColor(int color) {
+        float[] hsv = new float[3];
+        Color.colorToHSV(color, hsv);
+        hsv[2] *= DARKEN_COLOR_FRACTION;
+        return Color.HSVToColor(hsv);
+    }
+
+    /**
+     * Check which version of the drawables should be used depending on the given primary color.
+     * @param color The primary color value we are querying for.
+     * @return Whether the light colored text and drawable set should be used.
+     */
+    public static boolean shouldUseLightDrawablesForToolbar(int color) {
+        return getContrastForColor(color) >= CONTRAST_LIGHT_TEXT_THRESHOLD;
+    }
+
+    /**
+     * Check which version of the textbox background should be used depending on the given
+     * primary color.
+     * @param color The primary color value we are querying for.
+     * @return Whether the transparent version of the background should be used.
+     */
+    public static boolean shouldUseOpaqueTextboxBackground(int color) {
+        return getLightnessForColor(color) > LIGHTNESS_OPAQUE_BOX_THRESHOLD;
+    }
+}