Correct a small typo in WebGLRenderingContextBase::validateImageBitmap

At this moment, there is a line in the above function that has a small
typo in it, this CL corrects it.

Review URL: https://codereview.chromium.org/1639843002

Cr-Commit-Position: refs/heads/master@{#371582}

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

@@ -6556,7 +6556,7 @@ bool WebGLRenderingContextBase::validateHTMLVideoElement(const char* functionNam
 bool WebGLRenderingContextBase::validateImageBitmap(const char* functionName, ImageBitmap* bitmap, ExceptionState& exceptionState)
 {
     if (bitmap->isNeutered()) {
-        synthesizeGLError(GL_INVALID_VALUE, "texImage2D", "The source data has been neutered.");
+        synthesizeGLError(GL_INVALID_VALUE, functionName, "The source data has been neutered.");
         return false;
     }
     if (!bitmap->originClean()) {