SkPDF: Remove some unused glyphs from fallback fonts
SkPDF: Remove some unused glyphs from fallback fonts

This makes the /Widths and the /Differences arrays smaller.

Example diff in output PDF (lines are wrapped for easy viewing):

 <</Type /Font
 /Subtype /Type3
 /FontMatrix [.00100000005 0 0 -.00100000005 0 0]
 /FirstChar 0
-/LastChar 255
+/LastChar 118
 /FontBBox [23 228 669 -694]
 /CIDToGIDMap /Identity
 /ToUnicode 8 0 R
-/Widths [280 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
-525 0 0 0 525 0 0 0 0 525 525 525 525 0 0 0 0 0 0 525 0 0 0 0 0 0 0 0
-0 0 0 0 0 525 0 525 0 0 0 525 0 0 0 0 0 0 0 0 0 0 0 525 0 0 0 0 0 0
-525 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 525 0 0 0 0 0 0 0 525
-0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
-0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
-0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
-0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
+/Widths [280 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
+525 0 0 0 525 0 0 0 0 525 525 525 525 0 0 0 0 0 0 525 0 0 0 0 0 0 0 0
+0 0 0 0 0 525 0 525 0 0 0 525 0 0 0 0 0 0 0 0 0 0 0 525 0 0 0 0 0 0
+525 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 525 0 0 0 0 0 0 0
+525]
 /Encoding <</Type /Encoding
-/Differences [0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0
-/g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g1D
-/g0 /g0 /g0 /g21 /g0 /g0 /g0 /g0 /g26 /g27 /g28 /g29 /g0 /g0 /g0 /g0
-/g0 /g0 /g30 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g3E
-/g0 /g40 /g0 /g0 /g0 /g44 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0
-/g50 /g0 /g0 /g0 /g0 /g0 /g0 /g57 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0
-/g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g6E /g0 /g0 /g0
-/g0 /g0 /g0 /g0 /g76 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0
-/g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0
-/g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0
-/g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0
-/g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0
-/g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0
-/g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0
-/g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0
-/g0 /g0 /g0 /g0 /g0 /g0]>>
+/Differences [0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0
+/g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g1D
+/g0 /g0 /g0 /g21 /g0 /g0 /g0 /g0 /g26 /g27 /g28 /g29 /g0 /g0 /g0 /g0
+/g0 /g0 /g30 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g3E
+/g0 /g40 /g0 /g0 /g0 /g44 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0
+/g50 /g0 /g0 /g0 /g0 /g0 /g0 /g57 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0
+/g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g0 /g6E /g0 /g0 /g0
+/g0 /g0 /g0 /g0 /g76]>>
 /CharProcs <</g0 9 0 R
 /g1D 10 0 R
 /g21 11 0 R
.......

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2287393002

Review-Url: https://codereview.chromium.org/2287393002

rubenvb/skia,rubenvb/skia,Hikari-no-Tenshi/android_external_skia,rubenvb/skia,google/skia,HalCanary/skia-hc,google/skia,aosp-mirror/platform_external_skia,HalCanary/skia-hc,HalCanary/skia-hc,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,HalCanary/skia-hc,HalCanary/skia-hc,Hikari-no-Tenshi/android_external_skia,google/skia,rubenvb/skia,rubenvb/skia,rubenvb/skia,Hikari-no-Tenshi/android_external_skia,HalCanary/skia-hc,google/skia,HalCanary/skia-hc,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,Hikari-no-Tenshi/android_external_skia,HalCanary/skia-hc,HalCanary/skia-hc,Hikari-no-Tenshi/android_external_skia,google/skia,google/skia,Hikari-no-Tenshi/android_external_skia,aosp-mirror/platform_external_skia,rubenvb/skia,HalCanary/skia-hc,Hikari-no-Tenshi/android_external_skia,aosp-mirror/platform_external_skia,rubenvb/skia,google/skia,aosp-mirror/platform_external_skia,Hikari-no-Tenshi/android_external_skia,rubenvb/skia,rubenvb/skia