Fix logic error for GrTextBlob mustRegen

Change-Id: I2f08a3d26f411ef34d964a8f324696e97e8970ed
Reviewed-on: https://skia-review.googlesource.com/c/163162
Commit-Queue: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
Auto-Submit: Herb Derby <herb@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
diff --git a/src/gpu/text/GrTextBlob.cpp b/src/gpu/text/GrTextBlob.cpp
index 6249c3a..d96e046 100644
--- a/src/gpu/text/GrTextBlob.cpp
+++ b/src/gpu/text/GrTextBlob.cpp
@@ -196,8 +196,10 @@
             return true;
         }
 
-        if (!anyRunHasSubpixelPosition) {
-            // We can update the positions in the cachedtextblobs without regenerating the whole
+        // If the text blob only has full pixel glyphs, then fractional part of the position does
+        // not affect the SkGlyphs used.
+        if (anyRunHasSubpixelPosition) {
+            // We can update the positions in the text blob without regenerating the whole
             // blob, but only for integer translations.
             // This cool bit of math will determine the necessary translation to apply to the
             // already generated vertex coordinates to move them to the correct position.