NOTE:
On Windows & Linux OS after navigating to http://www.stepupnihongo.com/images/SUN3_L-51.pdf
-Font size is not properly displayed(i.e overlapping of text/alphabet is seen)

Please refer attached actual & expected screenshot 

Deleted: Actual_Win.png 321 KB

	Actual_Win.png 321 KB View Download

Deleted: Expected_Win.png 359 KB

	Expected_Win.png 359 KB View Download

Able to reproduce the issue and below are the bisect details obtained using per-revision bisect:

You are probably looking for a change made after 481560 (known good), but no later than 481561 (first known bad).
CHANGELOG URL: The script might not always return single CL as suspect as some perf builds might get missing due to failure.

https://chromium.googlesource.com/chromium/src/+log/a95e0bf52bfe99622e4bf498adb761cf9eb218a9..1545ba94087279c773705760d51b728d709fd72d

@dsinclair: Assigning to you, kindly take a look into it Please help us to find an owner if not with respect to your change.

Adding Blocker label, please decrease or remove priority if not the case.

Thanks.!

Looks like it picked a different font to use when rendering. Given the regression CL probably due to switching on Skia paths rendering.

This is a recent regression but it also happens to be broken in Stable so ReleaseBlock-Dev is not appropriate even if we hand't already disabled Skia paths. FYI this suggests my spacing CL [1] does not seem to be working properly when Skia paths is  enabled.
[1] https://pdfium-review.googlesource.com/c/6630/

CFX_SkiaDeviceDriver::DrawDeviceText seems to be ignoring the m_AdjustMatrix even when m_bGlyphAdjust is true, see for example
https://cs.chromium.org/chromium/src/third_party/pdfium/core/fxge/ge/cfx_renderdevice.cpp?type=cs&l=951

re #8 : thanks for the diagnosis -- very helpful

dsinclair@ turned off Skia path for PDFium, so this is no longer a P1 regression.

While this PDF does indeed use m_AdjustMatrix to condense characters, it mostly uses multiple master axis parameters to narrow the text in some places an embolden it in others.

The multiple master control code is in cfx_font.cpp, CFX_Font::AdjustMMParams.

I have a bit of rewriting to do to take advantage of this, and will work with our resident font expert to make sure that the result is sustainable.