Fix the crash of compressedTexImage3D for the WebGL2 conformance test page.

third_party/WebKit/Source/modules/webgl/WebGLTexture.cpp

Index: third_party/WebKit/Source/modules/webgl/WebGLTexture.cpp
diff --git a/third_party/WebKit/Source/modules/webgl/WebGLTexture.cpp b/third_party/WebKit/Source/modules/webgl/WebGLTexture.cpp
index 80d5bd122550a8930eb8e6535f6b55be582539e1..0da69183b33a70738d0afb3a4785a9934dd4e3ba 100644
--- a/third_party/WebKit/Source/modules/webgl/WebGLTexture.cpp
+++ b/third_party/WebKit/Source/modules/webgl/WebGLTexture.cpp
@@ -286,6 +286,18 @@ bool WebGLTexture::isValid(GLenum target, GLint level) const
     return info->valid;
 }
 
+bool WebGLTexture::isValidLevel(GLenum target, GLint level) const
+{
+    if (!object() || !m_target)
+        return false;
+    int targetIndex = mapTargetToIndex(target);
+    if (targetIndex < 0 || targetIndex >= static_cast<int>(m_info.size()))
+        return false;
+    if (level < 0 || level >= static_cast<GLint>(m_info[targetIndex].size()))
+        return false;
+    return true;
+}
+
 bool WebGLTexture::isNPOT(GLsizei width, GLsizei height)
 {
     ASSERT(width >= 0 && height >= 0);