Revert "Wrap page index packing in helper methods."

This reverts commit cb93a20d9a961219bad674d6c168bfde03a16246.

Reason for revert: Still seeing some corruption issues with Chrome text that may be related to this.

Original change's description:
> Wrap page index packing in helper methods.
> 
> Also simplifies the shaders if we know there's only one atlas texture.
> 
> Change-Id: I81063d423fd56cf91caee83ba9eae9d988aa249b
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/266566
> Commit-Queue: Jim Van Verth <jvanverth@google.com>
> Reviewed-by: Brian Osman <brianosman@google.com>

TBR=jvanverth@google.com,herb@google.com,brianosman@google.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: I031f27c07929b1f66581ed8e94e1056d9107bf75
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/266633
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
diff --git a/src/gpu/text/GrTextBlob.cpp b/src/gpu/text/GrTextBlob.cpp
index df9862d..c5f8797 100644
--- a/src/gpu/text/GrTextBlob.cpp
+++ b/src/gpu/text/GrTextBlob.cpp
@@ -253,8 +253,17 @@
 
         // We pack the 2bit page index in the low bit of the u and v texture coords
         uint32_t pageIndex = glyph->pageIndex();
-        std::tie(u0, v0) = GrDrawOpAtlas::PackIndexInTexCoords(u0, v0, pageIndex);
-        std::tie(u1, v1) = GrDrawOpAtlas::PackIndexInTexCoords(u1, v1, pageIndex);
+        SkASSERT(pageIndex < 4);
+        uint16_t uBit = (pageIndex >> 1u) & 0x1u;
+        uint16_t vBit = pageIndex & 0x1u;
+        u0 <<= 1u;
+        u0 |= uBit;
+        v0 <<= 1u;
+        v0 |= vBit;
+        u1 <<= 1u;
+        u1 |= uBit;
+        v1 <<= 1u;
+        v1 |= vBit;
 
         textureCoords[0] = u0;
         textureCoords[1] = v0;