Views: Add MRUCache of results from ShapeRunWithFont

Bookmark folders using Views are very janky (~5 fps, with the CPU
at 100%). Calls to RenderTextHarfBuzz::ShapeRunWithFont account for
almost all of this time.

Many of the calls to ShapeRunWithFont are done with the same arguments
every frame. To alleviate some of this jank, add a cache the results of
this function call.

Refactor RenderTextHarfBuzz::ShapeRunWithFont to be stateless, and add
structures ShapeRunWithFontInput and ShapeRunWithFontOutput for the
arguments and output of the function. Use ShapeRunWithFontInput as
a cache key.

Bug: 826265
Change-Id: Ic6726c1152c44dc5cb0eccddf1ff3adcd060d8e7
Reviewed-on: https://chromium-review.googlesource.com/1123456
Commit-Queue: ccameron <ccameron@chromium.org>
Reviewed-by: Trent Apted <tapted@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572420}

ui/gfx/font_render_params.cc

@@ -8,19 +8,6 @@
 
 namespace gfx {
 
-FontRenderParams::FontRenderParams()
-    : antialiasing(true),
-      subpixel_positioning(true),
-      autohinter(false),
-      use_bitmaps(false),
-      hinting(HINTING_MEDIUM),
-      subpixel_rendering(SUBPIXEL_RENDERING_NONE) {
-}
-
-FontRenderParams::FontRenderParams(const FontRenderParams& other) = default;
-
-FontRenderParams::~FontRenderParams() {}
-
 // static
 SkFontLCDConfig::LCDOrder FontRenderParams::SubpixelRenderingToSkiaLCDOrder(
     FontRenderParams::SubpixelRendering subpixel_rendering) {

ui/gfx/font_render_params.h

@@ -18,9 +18,13 @@ namespace gfx {
 
 // A collection of parameters describing how text should be rendered on Linux.
 struct GFX_EXPORT FontRenderParams {
-  FontRenderParams();
-  FontRenderParams(const FontRenderParams& other);
-  ~FontRenderParams();
+  bool operator==(const FontRenderParams& other) const {
+    return antialiasing == other.antialiasing &&
+           subpixel_positioning == other.subpixel_positioning &&
+           autohinter == other.autohinter && use_bitmaps == other.use_bitmaps &&
+           hinting == other.hinting &&
+           subpixel_rendering == other.subpixel_rendering;
+  }
 
   // Level of hinting to be applied.
   enum Hinting {
@@ -45,27 +49,27 @@ struct GFX_EXPORT FontRenderParams {
 
   // Antialiasing (grayscale if |subpixel_rendering| is SUBPIXEL_RENDERING_NONE
   // and RGBA otherwise).
-  bool antialiasing;
+  bool antialiasing = true;
 
   // Should subpixel positioning (i.e. fractional X positions for glyphs) be
   // used?
   // TODO(derat): Remove this; we don't set it in the browser and mostly ignore
   // it in Blink: http://crbug.com/396659
-  bool subpixel_positioning;
+  bool subpixel_positioning = true;
 
   // Should FreeType's autohinter be used (as opposed to Freetype's bytecode
   // interpreter, which uses fonts' own hinting instructions)?
-  bool autohinter;
+  bool autohinter = false;
 
   // Should embedded bitmaps in fonts should be used?
-  bool use_bitmaps;
+  bool use_bitmaps = false;
 
   // Hinting level.
-  Hinting hinting;
+  Hinting hinting = HINTING_MEDIUM;
 
   // Whether subpixel rendering should be used or not, and if so, the display's
   // subpixel order.
-  SubpixelRendering subpixel_rendering;
+  SubpixelRendering subpixel_rendering = SUBPIXEL_RENDERING_NONE;
 
   static SkFontLCDConfig::LCDOrder SubpixelRenderingToSkiaLCDOrder(
       SubpixelRendering subpixel_rendering);

ui/gfx/render_text_harfbuzz.h

@@ -76,8 +76,8 @@ struct GFX_EXPORT TextRunHarfBuzz {
   UBiDiLevel level;
   UScriptCode script;
 
-  std::unique_ptr<uint16_t[]> glyphs;
-  std::unique_ptr<SkPoint[]> positions;
+  std::vector<uint16_t> glyphs;
+  std::vector<SkPoint> positions;
   std::vector<uint32_t> glyph_to_char;
   size_t glyph_count;
 

ui/gfx/render_text_unittest.cc

@@ -3839,7 +3839,7 @@ TEST_P(RenderTextHarfBuzzTest, HarfBuzz_SubglyphGraphemePartition) {
   run.range = Range(0, 4);
   run.glyph_count = 2;
   run.glyph_to_char.resize(2);
-  run.positions.reset(new SkPoint[4]);
+  run.positions.resize(4);
   run.width = 20;
 
   RenderTextHarfBuzz* render_text = GetRenderTextHarfBuzz();