Fix SkiaRenderer WebGL content not show problem

The WebGL content is a flipped TextureQuad. SkiaRenderer only flips the
Y coordinate for drawImageRect(with canvas->scale(1, -1)). It will draw
the image outside of the Window (y < 0). To fix this problem, we use
canvas->translate(0, quad_rect.bottom()) to move it back into the
window.

Bug: 901822
Change-Id: I6b98f82fba896021e1c2878632b26a3bd8029845
Reviewed-on: https://chromium-review.googlesource.com/c/1324137
Commit-Queue: Peng Huang <penghuang@chromium.org>
Reviewed-by: danakj <danakj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606892}

components/viz/service/display/gl_renderer.cc

@@ -2379,9 +2379,7 @@ void GLRenderer::EnqueueTextureQuad(const TextureDrawQuad* quad,
   }
 
   // Generate the uv-transform
-  Float4 uv_transform = {{0.0f, 0.0f, 1.0f, 1.0f}};
-  if (!clip_region)
-    uv_transform = UVTransform(quad);
+  auto uv_transform = UVTransform(quad);
   if (sampler == SAMPLER_TYPE_2D_RECT) {
     // Un-normalize the texture coordiantes for rectangle targets.
     uv_transform.data[0] *= texture_size.width();

components/viz/service/display/skia_renderer.cc

@@ -739,8 +739,10 @@ void SkiaRenderer::DrawTextureQuad(const TextureDrawQuad* quad) {
   SkRect sk_uv_rect = gfx::RectFToSkRect(visible_uv_rect);
   SkRect quad_rect = gfx::RectToSkRect(quad->visible_rect);
 
-  if (quad->y_flipped)
+  if (quad->y_flipped) {
+    current_canvas_->translate(0, quad_rect.bottom());
     current_canvas_->scale(1, -1);
+  }
 
   bool blend_background =
       quad->background_color != SK_ColorTRANSPARENT && !image->isOpaque();