cc: Use highp precision for texture coords if available and needed

cc/output/shader_unittest.cc

Index: cc/output/shader_unittest.cc
diff --git a/cc/output/shader_unittest.cc b/cc/output/shader_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..adbe887113f1d6404f3a49b9f7792efe0c830686
--- /dev/null
+++ b/cc/output/shader_unittest.cc
@@ -0,0 +1,46 @@
+// Copyright 2013 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 "cc/output/shader.h"
+
+#include "cc/debug/fake_web_graphics_context_3d.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "ui/gfx/point.h"
+#include "ui/gfx/size.h"
+
+namespace cc {
+
+TEST(ShaderTest, HighpThresholds) {
+  // The FakeWebGraphicsContext3D always uses a mediump precision of 10 bits
+  // which corresponds to a native highp threshold of 2^10 = 1024
+  FakeWebGraphicsContext3D context;
+
+  int threshold_min;
+  gfx::Point closePoint(512, 512);
+  gfx::Size smallSize(512, 512);
+  gfx::Point farPoint(2560, 2560);
+  gfx::Size bigSize(2560, 2560);
+
+  threshold_min = 0;
+  EXPECT_EQ(TexCoordPrecisionMedium,
+            TexCoordPrecisionRequired(&context, threshold_min, closePoint));
+  EXPECT_EQ(TexCoordPrecisionMedium,
+            TexCoordPrecisionRequired(&context, threshold_min, smallSize));
+  EXPECT_EQ(TexCoordPrecisionHigh,
+            TexCoordPrecisionRequired(&context, threshold_min, farPoint));
+  EXPECT_EQ(TexCoordPrecisionHigh,
+            TexCoordPrecisionRequired(&context, threshold_min, bigSize));
+
+  threshold_min = 3000;
+  EXPECT_EQ(TexCoordPrecisionMedium,
+            TexCoordPrecisionRequired(&context, threshold_min, closePoint));
+  EXPECT_EQ(TexCoordPrecisionMedium,
+            TexCoordPrecisionRequired(&context, threshold_min, smallSize));
+  EXPECT_EQ(TexCoordPrecisionMedium,
+            TexCoordPrecisionRequired(&context, threshold_min, farPoint));
+  EXPECT_EQ(TexCoordPrecisionMedium,
+            TexCoordPrecisionRequired(&context, threshold_min, bigSize));
+}
+
+}