Simplify D1G so that it can inline DrawOneGlyph, and fix a bug in codegen

src/core/SkFindAndPlaceGlyph.h

Index: src/core/SkFindAndPlaceGlyph.h
diff --git a/src/core/SkFindAndPlaceGlyph.h b/src/core/SkFindAndPlaceGlyph.h
index 278be07e0b878538de9e5e7924d809be6fc1570f..bd6338d587448af77766122327e1236e6f531b99 100644
--- a/src/core/SkFindAndPlaceGlyph.h
+++ b/src/core/SkFindAndPlaceGlyph.h
@@ -30,6 +30,16 @@ struct SkMaxSizeOf<H, Ts...> {
         sizeof(H) >= SkMaxSizeOf<Ts...>::value ? sizeof(H) : SkMaxSizeOf<Ts...>::value;
 };
 
+
+// This is a temporary helper function to work around a bug in the code generation
+// for aarch64 (arm) on GCC 4.9. This bug does not show up on other platforms, so it
+// seems to be an aarch64 backend problem.
+//
+// GCC 4.9 on ARM64 does not generate the proper constructor code for PositionReader or
+// GlyphFindAndPlace. The vtable is not set properly without adding the fixme code.
+// The implementation is in SkDraw.cpp.
+extern void FixGCC49Arm64Bug(int v);
+
 class SkFindAndPlaceGlyph {
 public:
     template<typename ProcessOneGlyph>
@@ -229,6 +239,9 @@ private:
     public:
         virtual ~PositionReaderInterface() { }
         virtual SkPoint nextPoint() = 0;
+        // This is only here to fix a GCC 4.9 aarch64 code gen bug.
+        // See comment at the top of the file.
+        virtual int forceUseForBug() = 0;
     };
 
     class HorizontalPositions final : public PositionReaderInterface {
@@ -241,6 +254,8 @@ private:
             return {x, 0};
         }
 
+        int forceUseForBug() override { return 1; }
+
     private:
         const SkScalar* fPositions;
     };
@@ -256,6 +271,8 @@ private:
             return to_return;
         }
 
+        int forceUseForBug() override { return 2; }
+
     private:
         const SkScalar* fPositions;
     };
@@ -410,7 +427,9 @@ private:
     class GlyphFindAndPlaceSubpixel final : public GlyphFindAndPlaceInterface<ProcessOneGlyph> {
     public:
         GlyphFindAndPlaceSubpixel(LookupGlyph& glyphFinder)
-            : fGlyphFinder(glyphFinder) { }
+            : fGlyphFinder(glyphFinder) {
+            FixGCC49Arm64Bug(1);
+        }
 
         SkPoint findAndPositionGlyph(
             const char** text, SkPoint position, ProcessOneGlyph&& processOneGlyph) override {
@@ -464,6 +483,7 @@ private:
     public:
         GlyphFindAndPlaceFullPixel(LookupGlyph& glyphFinder)
             : fGlyphFinder(glyphFinder) {
+            FixGCC49Arm64Bug(2);
             // Kerning can only be used with SkPaint::kLeft_Align
             static_assert(!kUseKerning || SkPaint::kLeft_Align == kTextAlignment,
                           "Kerning can only be used with left aligned text.");
@@ -601,6 +621,7 @@ inline void SkFindAndPlaceGlyph::ProcessPosText(
             } else {
                 to_init->initialize<HorizontalPositions>(pos);
             }
+            positionReader->forceUseForBug();
         }
     };
 
@@ -617,7 +638,7 @@ inline void SkFindAndPlaceGlyph::ProcessPosText(
         }
     };
 
-    GlyphFindAndPlace<ProcessOneGlyph> findAndPosition{
+    GlyphFindAndPlace<ProcessOneGlyph> findAndPosition {
         [&](typename GlyphFindAndPlace<ProcessOneGlyph>::Variants* to_init) {
             if (cache->isSubpixel()) {
                 switch (textAlignment) {