Implement OES_texture_float_linear and OES_texture_half_float_linear extensions in WebGL.

Source/core/html/canvas/WebGLTexture.h

Index: Source/core/html/canvas/WebGLTexture.h
diff --git a/Source/core/html/canvas/WebGLTexture.h b/Source/core/html/canvas/WebGLTexture.h
index d766c3f617ed17a544c68bebff104612405fbc39..b1498f7b510c0386426f69e4679b993a01f4bce9 100644
--- a/Source/core/html/canvas/WebGLTexture.h
+++ b/Source/core/html/canvas/WebGLTexture.h
@@ -36,6 +36,11 @@ namespace WebCore {
 
 class WebGLTexture : public WebGLSharedObject {
 public:
+    enum TextureExtensionFlag {
+        NoTextureExtensionEnabled = 0,
+        TextureFloatLinearExtensionEnabled = 1,

[Ken Russell (switch to Gerrit), 2013/05/15 23:25:10]

It would be better to write these as 0, 1 << 0, and 1 << 1 to make it clear that
they're used as a bit field.

+        TextureHalfFloatLinearExtensionEnabled = 2
+    };
     virtual ~WebGLTexture();
 
     static PassRefPtr<WebGLTexture> create(WebGLRenderingContext*);
@@ -65,7 +70,7 @@ public:
 
     bool isNPOT() const;
     // Determine if texture sampling should always return [0, 0, 0, 1] (OpenGL ES 2.0 Sec 3.8.2).
-    bool needToUseBlackTexture() const;
+    bool needToUseBlackTexture(TextureExtensionFlag) const;
 
     bool hasEverBeenBound() const { return object() && m_target; }
 
@@ -124,6 +129,8 @@ private:
     bool m_isNPOT;
     bool m_isComplete;
     bool m_needToUseBlackTexture;
+    bool m_isFloatType;
+    bool m_isHalfFloatType;
 };
 
 } // namespace WebCore