Remove variable shadowing in blink/modules/webgl

In an effort to reduce or even ban variable shadowing, this renames
a variable to avoid such shadowing. I'm interested in prohibiting
shadowing because I think it might prevent potential jumbo problems.

The warnings this avoids is:
third_party/blink/renderer/modules/webgl/webgl_rendering_context_base.cc:3688:18: error: declaration shadows a local variable [-Werror,-Wshadow]
        unsigned length;
                 ^
third_party/blink/renderer/modules/webgl/webgl_rendering_context_base.cc:3658:13: note: previous declaration is here
    GLsizei length = 0;
            ^
third_party/blink/renderer/modules/webgl/webgl_rendering_context_base.cc:5234:31: error: declaration shadows a local variable [-Werror,-Wshadow]
      ScopedTexture2DRestorer restorer(gl);
                              ^
third_party/blink/renderer/modules/webgl/webgl_rendering_context_base.cc:5190:27: note: previous declaration is here
  ScopedTexture2DRestorer restorer(this);

Bug: 923510
Change-Id: Idef0b7f4b47aad7c0199d9e11571dc93d1c94429
Reviewed-on: https://chromium-review.googlesource.com/c/1477679
Commit-Queue: Kentaro Hara <haraken@chromium.org>
Auto-Submit: Daniel Bratell <bratell@opera.com>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#633750}

third_party/blink/renderer/modules/webgl/webgl_rendering_context_base.cc

@@ -3674,15 +3674,15 @@ ScriptValue WebGLRenderingContextBase::getUniform(
     LChar* name_ptr;
     scoped_refptr<StringImpl> name_impl =
         StringImpl::CreateUninitialized(max_name_length, name_ptr);
-    GLsizei length = 0;
+    GLsizei name_length = 0;
     GLint size = -1;
     GLenum type = 0;
-    ContextGL()->GetActiveUniform(program_id, i, max_name_length, &length,
+    ContextGL()->GetActiveUniform(program_id, i, max_name_length, &name_length,
                                   &size, &type,
                                   reinterpret_cast<GLchar*>(name_ptr));
     if (size < 0)
       return ScriptValue::CreateNull(script_state);
-    String name(name_impl->Substring(0, length));
+    String name(name_impl->Substring(0, name_length));
     StringBuilder name_builder;
     // Strip "[0]" from the name if it's an array.
     if (size > 1 && name.EndsWith("[0]"))
@@ -5250,7 +5250,7 @@ void WebGLRenderingContextBase::TexImageViaGPU(
       WebGLRenderingContextBase* gl = source_canvas_webgl_context;
       if (gl->is_origin_top_left_ && !canvas()->LowLatencyEnabled())
         flip_y = !flip_y;
-      ScopedTexture2DRestorer restorer(gl);
+      ScopedTexture2DRestorer inner_restorer(gl);
       if (!gl->GetDrawingBuffer()->CopyToPlatformTexture(
               ContextGL(), target, target_texture, unpack_premultiply_alpha_,
               !flip_y, IntPoint(xoffset, yoffset), source_sub_rectangle,