Remove stale todo since Chromium no longer uses analysis canvas

With cc: Add solid color analyzer to replace AnalysisCanvas,
https://chromium-review.googlesource.com/c/chromium/src/+/538974/

Solid color analysis is run directly on a paint op buffer instead of
rasterizing to a skia::AnalysisCanvas. This change hence removes
stale comment that refers to optimizing AnalysisCanvas.

Change-Id: Ic87d6e056596713b85882abadbd278bf866ab3dd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1860675Reviewed-by: Khushal <khushalsagar@chromium.org>
Commit-Queue: Khushal <khushalsagar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#705864}

cc/tiles/tile_manager.cc

@@ -701,8 +701,6 @@ TileManager::PrioritizedWorkToSchedule TileManager::AssignGpuMemoryToTiles() {
         tile->use_picture_analysis() && kUseColorEstimator) {
       // We analyze for solid color here, to decide to continue
       // or drop the tile for scheduling and raster.
-      // TODO(sohanjg): Check if we could use a shared analysis
-      // canvas which is reset between tiles.
       tile->set_solid_color_analysis_performed(true);
       SkColor color = SK_ColorTRANSPARENT;
       bool is_solid_color =